The things in the passage were hidden until the N.T. and revealed to believers through the Spirit.
the object of the apostle is not to describe the future state of the redeemed. It is to prove that those who are Christians have true wisdom
1 Corinthians 2:6-7; or that they have views of truth, and of the excellence of the plan of salvation which the world has not, and which those who crucified the Lord Jesus did not possess. The thing which he is describing here, is not merely the happiness of Christians, but their views of the wisdom of the plan of salvation. They have views of that which the eyes of other people have not seen; a view of wisdom, and fitness, and beauty which can be found in no other plan. It is true that this view is attended with a high degree of comfort; but the comfort is not the immediate thing in the eye of the apostle.
the declaration in
1 Corinthians 2:10, is conclusive proof that Paul does not refer to the happiness of heaven. He there says that God has revealed these things to Christians by his Spirit. But if already revealed, assuredly it does not refer to that which is yet to come. But although this does not refer directly to heaven, there may be an application of the passage to a future state in an indirect manner, which is not improper. If there are such manifestations of wisdom in the plan here; if Christians see so much of its beauty here on earth; and if their views so far surpass all that the world sees and enjoys, how much greater and purer will be the manifestations of wisdom and goodness in the world of glory.
Eye hath not seen - This is the same as saying, that no one had ever fully perceived and understood the value and beauty of those things which God has prepared for his people. All the world had been strangers to this until God made a revelation to his people by his Spirit. The blessedness which the apostle referred to had been unknown alike to the Jews and the Gentiles.
Nor ear heard - We learn the existence and quality of objects by the external senses; and those senses are used to denote any acquisition of knowledge. To say that the eye had not seen, nor the ear heard, was, therefore, the same as saying that it was not known at all. All people had been ignorant of it. Neither have entered into the heart of man - No man has conceived it; or understood it. It is new; and is above all that man has seen, and felt, and known. barnes
hope this helps !!!