But to this one I will look,
To him who is humble and contrite of spirit,and
who trembles at My word (Isaiah 66:2).

This was Isaiah's assessment of what's important, namely, to be humble and repentant and to revere God's Word. The prophet Micah was Isaiah's contemporary among the common people. This was his assessment of what's important:

He has told you, O man, what is good;
And what does the Lord require of you
But to do justice, to love kindness,
And to walk humbly with your God? (Micah 6:8).

Justice and kindness (or mercy) summarize the Law of God, which the apostle Paul would later write is captured in the one command, "Love your neighbor as yourself" (Galatians 5:14).

Therefore, humility and reverent obedience to God's Word is what is of central importance for every believer. Solomon would give the same assessment after twelve chapters of depicting the vanity in everything else:

The conclusion, when all has been heard, is: fear God and keep His commandments, because this applies to every person (Eccelesiastes 12:13).

Our Lord Jesus would reaffirm this central purpose:

But seek first His kingdom and His righteousness, and all these things will be added to you (Matthew 6:33).

Friends, why do we complicate the Christian life. Is it not simply to humbly trust God and obey His Word? Is it not to make His priority our priority, His desires our desires, His will our will? Yet, we often get caught up in our worldly ambition, our quest for temporal excellence and our enjoyment of all aspects of earthly life. We give precious little time to His Word, which God commanded in both testaments to be the focal point of our thoughts and plans. Rather than transforming our every mundane experience into a spiritual act of worship, we compromise and accomodate God's principles to indulge our worldly passions. If we reflect but a moment, we would see our inconsistency, even our hypocrisy. May the Lord help us live the reality of the faith He has granted us according to the incomparable riches of His grace.

I permitted Myself to be sought by those who did not ask for Me;
I permitted Myself to be found by those who did not seek Me.
I said, "Here am I, here am I,"
To a nation which did not call on My name.

I have spread out My hands all day long to a rebellious people,
Who walk in the way which is not good, following their own thoughts (Isaiah 65:1-2).

This passage is cited in Romans 10:20-21, where Paul argues that even though people universally heard the message, this hearing was not combined with faith. Israel heard and understood, but they did not believe. So God allowed Himself to be found by those (i.e. Gentiles) who did not ask, seek or call upon Him. He did this because those that knew Him and should have believed in Him, instead rejected Him. As Isaiah writes,

Because I called, but you did not answer;
I spoke, but you did not hear (Isaiah 65:12).

It is because of this persistent unbelief by Israel that God has opened the floodgates of faith to the Gentiles. So Paul writes,

Because of their transgression, salvation has come to the Gentiles (Romans 11:11). 

Israel has experienced a hardening in part until the full number of the Gentiles has come in (Romans 11:25).

Now, there will also be a future restoration of national Israel on the basis of His irrevocable promises to the Patriarchs (cf. Romans 11:25-32).

Therefore, let us understand that God was not surprised by the spiritual ignorance of the nations, who did not call upon Him, and the rebellion of His own people, who would not call upon Him, for the Bible says that this too was by His design. He did this so that whether they knew Him or not, it would be clear that the only way anyone would be saved would be by the grace of God:

For God has bound everyone over to disobedience so that he may have mercy on them all (Romans 11:32).

Paul explains this again in Ephesians 2, where he argues that both Gentiles ("you") and Jews ("us") are all captive to disobedience and deserving of wrath:

As for you [i.e. Gentiles], you were dead in your transgressions and sins, in which you used to live when you followed the ways of this world and of the ruler of the kingdom of the air, the spirit who is now at work in those who are disobedient. All of us [Jews] also lived among them at one time, gratifying the cravings of our flesh and following its desires and thoughts. Like the rest, we were by nature deserving of wrath (Ephesians 2:1-3).

In this seemingly hopeless scenario for all mankind, whether Jews or Gentiles, God sovereignly entered the equation with the message and power of His grace through Jesus Christ:

But because of his great love for us, God, who is rich in mercy, made us alive with Christ even when we were dead in transgressions—it is by grace you have been saved (Ephesians 2:4).

This is in keeping with Isaiah's premise that God was given to those that did not ask for Him. He was found by those that did not seek Him. This is represented in Paul's words, "dead in transgressions". Paul clearly meant spiritually dead here because both the Gentiles to whom he wrote and he himself were still physically alive when he wrote these words. Can someone spiritually dead (i.e. absent the Spirit that gives life) believe? Certainly not! Spiritually dead means spiritually blind. Spiritually dead means spiritually deaf. Spiritually dead means incapable of saving faith. This is why Jesus also said,

This is why I told you that no one can come to me unless the Father has enabled them (John 6:65).

Paul writes that God "made us alive." This is a precursor to faith. It was through regeneration that we are able to hear the Gospel message so as to believe, and regeneration is a sovereign work of God through His Spirit (cf. John 3:3-8). But apart from the spiritual discernment that comes from God's Holy Spirit, we would never embrace the foolishness of the message of the cross so as to believe and be saved (cf. 1 Corinthians 2:9-14).

Friends, we need to take God's words to heart:

But to this one I will look,
To him who is humble and contrite of spirit, and who
trembles at My word (Isaiah 66:2).

Therefore, since we know what God has sovereignly accomplished for us and in us apart from any effort or willing on our part, let us humbly work out this salvation with an attitude of fear and trembling, knowing that even in our sanctification, God is still working and willing to sovereignly and perfectly complete what He alone began in us:

Continue to work out your salvation with fear and trembling, for it is God who works in you to will and to act in order to fulfill his good purpose (Philippians 2:12-13).

Being confident of this, that he who began a good work in you will carry it on to completion until the day of Christ Jesus (Philippians 1:6).

You welcome those who gladly do good, who follow godly ways. But you have been very angry with us, for we are not godly. We are constant sinners; how can people like us be saved? We are all infected and impure with sin. When we display our righteous deeds, they are nothing but filthy rags. Like autumn leaves, we wither and fall, and our sins sweep us away like the wind. Yet no one calls on your name or pleads with you for mercy. Therefore, you have turned away from us and turned us over to our sins. And yet, O LORD, you are our Father. We are the clay, and you are the potter. We all are formed by your hand. (Isaiah 64:5-8 NLT)

This is Isaiah's plee to God for mercy. He acknowledges the sinfulness of the people, among whom he does not exclude himself. He does not say "they..." but "we..." in order to include himself. So, in view of this universal sinfulness, Isaiah's asks, "How can people like us be saved?" His answer begins with their helplessness and God's sovereignty: "We are the clay, you are the potter." What is Isaiah's point? He is saying that there is no possible way for us to save ourselves, for our righteousness will always come short ("they are nothing but filthy rags"); therefore, if we are to be saved, God must do it unilaterally and sovereignly, even as He did in birthing and forming us, as a Father and as a Potter. 

Friends, let us all have such a view of ourselves, always confessing our inability but, with humble and contrite hearts, acknowledging God's grace in His sovereignty, whereby He chooses to save some of us, not for anything in us, but simply for His Name's sake. 

Now, if we are chosen by God, what sort of people should we be? Not those that continue to forge our own righteousnessness through empty rituals and sacrifices, but those who, with humble and contrite hearts, tremble at God's Word:

My hands have made both heaven and earth; they and everything in them are mine. I, the LORD, have spoken! “I will bless those who have humble and contrite hearts, who tremble at my word. But those who choose their own ways—delighting in their detestable sins—will not have their offerings accepted. When such people sacrifice a bull, it is no more acceptable than a human sacrifice. When they sacrifice a lamb, it’s as though they had sacrificed a dog! When they bring an offering of grain, they might as well offer the blood of a pig. When they burn frankincense, it’s as if they had blessed an idol. (Isaiah 66:2, 3 NLT)

It is this same kind of humbling of ourselves and trembling obededience to God that Paul exhorts in his letter:

Your attitude should be the same as that of Christ Jesus: Who, being in very nature God, did not consider equality with God something to be grasped, but made himself nothing, taking the very nature of a servant, being made in human likeness. And being found in appearance as a man, he humbled himself and became obedient to death– even death on a cross! Therefore, my dear friends, as you have always obeyed–not only in my presence, but now much more in my absence–continue to work out your salvation with fear and trembling, for it is God who works in you to will and to act according to his good purpose. (Philippians 2:5-8, 12, 13 NIV84)

Friends, notice that I always try to find New Testament principles that reflect Old Testament teaching. I hope you consider this a rule of thumb for your own applications of Scripture. We are New Testament (i.e. New Covenant) believers; therefore, much of the Old Testament has only indirect application to us. The New Testament must always serve as a kind of filter and confirmation for the Old Testament principles in order for us to properly make any direct applications to our lives. 

Isaiah 65
20No more shall there be in it
   an infant who lives but a few days,
   or an old man who does not fill out his days,
for the young man shall die a hundred years old,
   and the sinner a hundred years old shall be accursed.

I read this and paused to challenge my view that we will live on a new Earth, as immortals, never to die. But if this numbers our days to an end, how can immortality be deduced?
We are promised eternal life through Jesus christ, but perhaps this 'spiritual' in nature. But jesus also spoke of a physical resurrection, but perhaps we will live longer than Adam, and then to spiritually to live eternally.
But I recalled hearing 'imperishable' in scripture: which lead me to:
1 corinthians 15:53
53For this perishable body must put on the imperishable, and this mortal body must put on immortality.

So this passage in Isaiah is in literary use, not literal. The proceeding verses speak of us living with the longevity of trees! In other words, forever!

Yujin responds... There is another explanation. Remember, the Book of Revelation speaks of a Millennial Kingdom prior to the advent of the New Heaven and the New Earth. This Millennial Kingdom will last 1000 years. Thus, the people that are born into this kingdom may be the ones in view that will have these very long lives.

All day long I have held out my hands
to an obstinate people,
who walk in ways not good,
pursuing their own imaginations

 God says we all seek after our own imaginations. They would've been idols of the neighboring nations of Israel in Isaiah's time. But in our days, those may include different religions and philosophies that are used to explain the reason for our sufferings, science that we claim to be the author of the nature, moralism of our own standard to define good and evil, and so forth. We do not want our Father in our lives. We are adamantly defiant to God in every single possible way. Even the default of the defiance is not contrite heart as one may think but indifference toward Him. We are utterly depraved of His goodness due to our sin. If it were not for God's zeal to save His chosen ones, this world would be like Sodom and Gomorrah! I humble myself again before the Almighty for His sovereignty and love that make His hands held out for us. God who no eyes have seen and who no ears have heard is our Father! Praise Him forever!