I was ready to be sought by those who did not ask for me; I was ready to be found by those who did not seek me. I said, “Here I am, here I am,” to a nation that was not called by my name.
The apostle Paul (an expositor we may depend upon) has given us the true sense of these verses, and told us what was the event they pointed at and were fulfilled in, namely, the calling in of the Gentiles and the rejection of the Jews, by the preaching of the gospel, Rom 10:20, Rom 10:21.
Commenting on Isaiah 65:1-7
I am sought of them that asked not for me,.... That this is a prophecy of the calling and conversion of the Gentiles is not to be doubted, since the Apostle Paul has quoted it, and applied it to that case, Rom 10:20 and is here mentioned as an aggravation of the sin of the Jews, in rejecting Christ, when the Gentiles received him; and...
I am sought by [them that] asked not [for me]; I am found by [them that] sought me not: I said, Behold me, behold me, to a nation [that] was not called by my name. (a) Meaning, the Gentiles who know not God, would seek him, when he had moved their heart with his Holy Spirit, .