This world is often a very harsh place, sometimes barely survivable. In ancient times whole civilizations were crushed, a family in the wrong place at the wrong time only seeking to survive in relative peace could be wiped out by war or famine or disease or criminality. So widespread and typical, it was impossible for ancient man to imagine anything different. But God's people, Israel, received promises from God. If they would be faithful, their lives here would be so much more pleasant. God would bless them. Famines would cease in the land; they would be protected from their enemies; their crops and herds and flocks would be productive. When the nation was faithful, God kept His promise and blessed them and prospered them. Many of the Psalms written during these prosperous times speak of the blessings they enjoyed for the times they remained faithful.

You know what God told them? In effect, He told them that they “had not seen anything yet!” This promise was meant to build anticipation and excitement. As wonderful as God's blessings had been, they were nothing compared to what was to come. They might have wondered, having been blessed with land, health, food, and security from their enemies, “But what more could one want?”

Since The Beginning of the World
Yes, God had blessed the nation, but the people had forsaken Him. So now, during the days of Isaiah, the Lord had withdrawn from His people. Theirs had become a truly “god-forsaken land” and there seemed to be nothing but destruction on the horizon. Their cities and even the temple where God had once been worshipped now lay in ruins (Isaiah 64:10,11).

Yes, there had been periods of righteousness in the past, but the righteousness of the nation in the past did nothing for the people of Isaiah's day (Isaiah 64:6,7) . One who would compromise and try to serve both God and idols might as well not call upon God at all because He will not hear.

Israel and Judah had turned to immorality and idolatry. But it was only Jehovah that had actually done something for the people. The idols had not. So why turn to them (Isaiah 64:3-5)?

It is hard to believe that a nation would forsake a God that had actually done these things for them. Why? Would people really do such a thing? Perhaps we could ask the same question of our own generation. We have been a blessed nation founded upon principles that are righteous by believers in God. And yet, we are forsaking the very God of whom our founders wrote insisting it was He who gave us rights and liberty and prayed to Him daily.

Note Isaiah 64:4 again: “For from days of old they have not heard or perceived by ear, Nor has the eye seen a God besides You, Who acts in behalf of the one who waits for Him.”

God is unique. There is no replacement. Not for nations and not for individuals, and not for you. Human ears have not heard and human eyes have not seen any other God who will “act in behalf of one who waits on Him”.

But We Have Seen God Who Will Act In Behalf of Those That Love Him
Though it is not an exact quote of what Isaiah had written seven centuries before, Paul uses Isaiah's words to say something similar; specifically that we have a God who acts in behalf of those who love Him.
“But just as it is written, 'Things which eye has not seen and ear has not heard, And which have not entered the heart of man, All that God has prepared for those who love Him.'“ (1 Corinthians 2:9)

We find at least two important truths as we compare the context of these two passages; Isaiah 64:4 and 1 Corinthians 2:9.

First, notice the two parallel phrases “from days of old” and “before the ages” (1 Corinthians 2:7). This “mystery” is not something that remains a mystery. Isaiah knew that unlike idols, the living God intervenes, so that was not a mystery. The “mystery” part was exactly how God would intervene to take away sins… theirs and ours (Isaiah 64:5b; 9; 12). Could the people of Isaiah's have possibly fathomed what God would do through Jesus at the cross? But now, through the gospel, we do know these things which never entered their hearts (1
Corinthians 2:10-13; Colossians 1:25-28).

Second, note the two phrases “Who acts in behalf of the one who waits for Him” and “All that God has prepared for those who love Him”. The one who “waits” for God is parallel to those “who love Him”. Our ability to endure life, survive and even prosper with joy and peace, growing in our faith (waiting for the Lord - not giving up) is depended in part on how much we love God and appreciate His grace and blessings. If you really love someone, your loyalty to them will have no limits! Besides that, we know what God has prepared for those that love Him. Paul
“waited for the Lord” (2 Timothy 4:7) and Paul loved the Lord (2 Timothy 4:8). Human ears have not heard and human eyes have not seen any other God who will
“act in behalf of one who waits on Him”.

Conclusion
There is a sense in which we have yet to see eternity's place for the faithful. We see it by faith; we know certain aspects of it by revelation, but it is still outside of our experience at this time. There are characteristics and attributes of the eternal state which are described for us in terms we can relate to. One of my favorites is found here: (Revelation 21:1-4).

And yet, I understand that this is a vision of heavenly scenes which employ symbols of another realm or state of existence. Things that flesh and blood cannot inherit. Things we probably cannot imagine. In that way, perhaps we can take the words that Paul once used concerning the mystery of the gospel and still say, applying them to heaven: 'Things which eye has not seen and ear has not heard, And which have not entered the heart of man, All that God has prepared for those who love Him.'“