Break up your fallow ground,
And do not sow among thorns.
Circumcise yourselves to the Lord
And remove the foreskins of your heart (Jeremiah 4:3).

This Scripture reminds me of an old song by a Christian band called Petra:
https://youtu.be/lP_XNlt8Opk. Here are the lyrics:

More lyrics: http://www.lyricsmode.com/lyrics/p/petra/

This section of Jeremiah begins with this counsel from the LORD:

"If you will return, O Israel,” declares the Lord,
"Then you should return to Me (Jeremiah 4:1).

What's the problem? The next chapter provides the answer:

But they refused to take correction.
They have made their faces harder than rock;
They have refused to repent (Jeremiah 5:3).

The people of Judah had made the soil of their hearts hard, so that nothing could grow in it (cf. Jeremiah 5:23). The surrounding context suggests that they had surrounded themselves with leaders and teachers that told them just what they wanted to hear but not what they needed to hear (cf. Jeremiah 5:12-13, 30-31; 6:13-14). They had made themselves morally stupid, ignorant of righteousness, and desensitized to evil:

"For My people are foolish,
They know Me not;
They are stupid children
And have no understanding.
They are shrewd to do evil,
But to do good they do not know (Jeremiah 4:22).

“Were they ashamed because of the abomination they have done?
They were not even ashamed at all;
They did not even know how to blush (Jeremiah 6:15).

It is in this condition that God tells them to break up the fallow ground of their hearts. Otherwise, they would be like those who have ears but cannot hear and those who have eyes but cannot see:

Now hear this, O foolish and senseless people,
Who have eyes but do not see;
Who have ears but do not hear (Jeremiah 5:21).

Friends, what lesson can we take from this oracle of judgment spoken to the people of Judah, which was given right before their destruction at the hands of Babylon?

It is not simply to acknowledge God's righteous commands. There is that. But there is something even more basic. It is to plow our hearts, so that the soil of our hearts may be fertile and not fallow. If the soil of our hearts are hard, and we are unteachable and wise in our own eyes, then how can God's Word take root and produce fruit in us.

Thus, we also learn this truth from Jesus' parable about the soils, which is only one of a handful of Jesus' many parables that made it into all three gospels (cf. Matthew 13:1-23; Mark 4:1-20; Luke 18:1-15) and certainly the most extensively explained. In this parable Jesus taught the importance of a heart receptive to the planted Word of God. The heart that is deceived by Satan's schemes will not be fruitful. The heart that is swayed by popular opinion will not be fruitful. The heart that is more concerned with worldly cares and gains will not fruitful. No, it is the heart, that listens to God's Word, understands it, and accepts it - it is this kind of soil and heart that will be fruitful.

Therefore, friends, let us humble ourselves before God's Word. Let us not be found manipulating it to serve our own ends. Let us not simply hear what we want to hear from God's Word and ignore the rest but seek to understand the whole counsel of Scripture. Let us not be wise in our own eyes so that we refuse correction. Let us not confuse worldly peace with the peace of God. Let us not mistaken God's Word for our own thoughts. Let us not entrust our eternal destinies and Christian walk to pastors, teachers or anyone else but take responsibility for ouselves, even to properly read and understand God's Word for ourselves. When we do receive preaching and teaching, let us test every word and verify from Scripture that it is true. And let us train our hearts to hear and do and not simply to hear and nod our heads in agreement.

It is in taking responsibility for ourselves in learning God's Word and training our hearts in consistent obedience to it that we break up the fallow ground of our hearts.

Now, if you find this hard, be encouraged, dear friends, for we have this promise from the Lord, that whatever our progress in this endeavor, God will complete the work He began in us in the fullness of time (cf. Philippians 1:6; 1 Thessalonians 5:23-24). But for this let us not be lazy in well-doing. 

"Go up and down the streets of Jerusalem, look around and consider, search through her squares. If you can find but one person who deals honestly and seeks the truth, I will forgive this city. Although they say, 'As surely as the Lord lives, 'still they are swearing falsely." Lord, do not your eyes look for truth? You struck them, but they felt no pain; you crushed them, but they refused correction. They made their faces harder than stone and refused to repent. I thought, "These are only the poor; they are foolish, for they do not know the way of the Lord, the requirements of their God. So I will go to the leaders and speak to them; surely they know the way of the Lord, the requirements of their God. "But with one accord they too had broken off the yoke and torn off the bonds. Hear this, you foolish and senseless people, who have eyes but do not see, who have ears but do not hear: The prophets prophesy lies, the priests rule by their own authority, and my people love it this way. But what will you do in the end? (Jeremiah 5:1-5, 21, 31 NIV)

To whom can I speak and give warning? Who will listen to me? Their ears are closed so they cannot hear. The word of the Lord is offensive to them; they find no pleasure in it. "From the least to the greatest, all are greedy for gain; prophets and priests alike, all practice deceit. They are all hardened rebels, going about to slander. They are bronze and iron; they all act corruptly. The bellows blow fiercely to burn away the lead with fire, but the refining goes on in vain; the wicked are not purged out. (Jeremiah 6:10, 13, 28, 29 NIV)

Friends, the debate surrounding election and free will is not simply about one's view of certain verses on predestination, but it also reflects one's view of oneself and mankind. If you have a high view of mankind, that there is innate righteousness in us, then you can easily accept the premise that by our own free will we can choose God and the righteousness offered in Christ. However, if you believe that no one has any innate righteousness ("not even one person"), that no one seeks the truth ("not even one person"), that people are foolish and senseless, having eyes but failing to see, ears but failing to hear, then you will understand that apart from God's sovereign election in salvation, we have no hope at all. 

People that believe in free will (in salvation) must contend with verses like those above, which are reflected in New Testament passages like Romans 3:1-9 and Ephesians 2:1-10 and 1 Corinthians 2:14, which clearly say that the person without the Spirit cannot accept nor even understand spiritual truths, of which the Gospel is certainly the chief. Now, you may say that there are plenty of verses that call people to choose God. Yes, but the argument is not against people choosing, but that left to themselves, people simply WILL NOT choose God. We contend that unless God first chooses us, we would never choose Him. Unless the Spirit first works in us, even to give us eyes to see, we could never see the kingdom of God. Therefore, while all can agree that people CAN choose Christ, the biblical evidence strongly argues that no one WILL choose Christ. Why? it is because of human depravity, even a fallen nature that has corrupted the will, so that it is enslaved to a lie.

Now, the only argument that I cannot satisfactorily answer is why God does not give everyone eyes to see. Since we are all needy, why not save us all. But He chooses to justly judge the vast majority of humanity and be generous with a relatively select few. When I search the Bible for answers, I only get two somewhat disturbing ones. First, I have no business questioning God's motives, even as the clay cannot talk back to the Potter. Second, God is glorified in both the salvation of some as well as the destruction of many. 

I would not proclaim the Gospel as the most reasonable or compassionate religion. It is not necessarily so. I proclaim it simply because I believe it is the truth. And if it is true, we ought to believe it. At the same time, I recognize that only those that have been given eyes to see and ears to hear will, in fact, believe it. This realization does not hinder me one bit from proclaiming the Gospel, but it removes any delusion that I am saving anyone, and it converts my motivation from saving people to simply obeying God's command. 

Having the perspective of Isaiah and Paul, that "no one is righteous, not even one," makes me absolutely humble, for I would certainly not choose to be humble of myself. For I can never say, "I am a better person than that person, and that is why God saved me." I can never say that I was wiser for choosing God over someone else, who was foolish for rejecting God. But I would recognize that given the right conditions, I too could have been as bad as Hitler, as cruel as Stalin, or as warped as Bin Ladin. In fact, in some respects, I am as they are, and they are as I am, namely, sinful, blind, and deserving only of eternal condemnation for offending an eternal and holy God. But praise God He has saved me! And, my friends, praise God He has saved you!

This is why there is no boasting in the Gospel - none whatsoever - not in our works, not in our faith, not in anything. Our one and only boast, therefore, is the one shared by every believer, and it is simply in our Lord and God, who has chosen to save us. 

Friends, in these chapters we have a strong indictment of the people of Judah as the days of their Babylonian exile approaches. These are God's final appeals to the people to return to Him. They have embraced His benefits and become rich, but instead of trusting him more and being more obedient to Him, they have become self-confident, self-indulgent, embracing only those prophets and priests that support their indulgent behavior. Consider just some of these indictments:

For My people are foolish,
They have not known Me.
They are silly children,
And they have no understanding.
They are wise to do evil,
But to do good they have no knowledge (Jeremiah 4:22).

O LORD, are not Your eyes on the truth?
You have stricken them,
But they have not grieved;
You have consumed them,
But they have refused to receive correction.
They have made their faces harder than rock;
They have refused to return (Jeremiah 5:3).

How shall I pardon you for this?
Your children have forsaken Me
And sworn by those that are not gods.
When I had fed them to the full,
Then they committed adultery
And assembled themselves by troops in the harlots' houses.
They were like well-fed lusty stallions;
Every one neighed after his neighbor's wife (Jeremiah 5:7-8).

For among My people are found wicked men;
They set a trap;
They catch men.
As a cage is full of birds,
So their houses are full of deceit.
Therefore they have become great and grown rich.
They have grown fat, they are sleek;
Yes, they surpass the deeds of the wicked;
They do not plead the cause,
The cause of the fatherless;
Yet they prosper,
And the right of the needy they do not defend (Jeremiah 5:26-28).

The prophets prophesy falsely,
And the priests rule by their own power;
And My people love to have it so.
But what will you do in the end? (Jeremiah 5:31).

Because from the least of them even to the greatest of them,
Everyone is given to covetousness;
And from the prophet even to the priest,
Everyone deals falsely (Jeremiah 6:13).

This section ends with the strong pronouncement, "the LORD has rejected them" (Jeremiah 6:30). While the LORD has rejected His people in their sinfulness and will exile them into captivity, we understand that He has not completely rejected them. So we read in verses like Jeremiah 4:27, "The whole land shall be desolate; Yet I will not make a full end" and in Jeremiah 5:18, "Neverthless in those days...I will not make a complete end of you." There will be preserved by God a small remanant with whom He will fulfill His promises to Abraham and to David.

This should be a sobering message to all of us as well. Among the peoples of the world, with perhaps little exception, only the Jews were "saved." But even among the Jews, only a small remnant from them were "saved." Today may not be much different. In the world at large, only the Christians are "saved." But among Christians, I daresay only a small remnant of them will be "saved."  Paul wrote, "Faith comes by hearing, and hearing by the Word of God" (Romans 10:17). Oftentimes, this "Word of God" is treated as the Bible, but in this rhetorical context of point and counterpoint in Romans 10, I believe what is in view is God's decree. Paul argues that when the Gospel was preached, no one heard. Why? Because they did not have ears to hear; that is, they did not have the faith to accompany hearing, so that their hearing would be effective. But by God's decree faith was given so that their ears could be "circumcised," and they could hear. As Jeremiah wrote also,

Hear, O earth!
Behold, I will certainly bring calamity on this people --
The fruit of their thoughts,
Because they have not heeded My words
Nor My law, but rejected it (Jeremiah 6:19).

To whom shall I speak and give warning,
That they may hear?
Indeed their ear is uncircumcised,
And they cannot give heed.
Behold, the word of the LORD is a reproach to them;
They have no delight in it (Jeremiah 6:10).

Therefore, those of us who have been given ears to hear, let us diligently hear and then heed, listen and then do, read and then obey. As we do these things, we will make our calling and election to salvation sure (2 Peter 1:10).