But the angel said unto him, Fear not, Zacharias: for thy prayer is heard; and thy wife Elizabeth shall bear thee a son, and thou shalt call his name John. And thou shalt have joy and gladness; and many shall rejoice at his birth. For he shall be great in the sight o the Lord, and shall drink neither wine nor strong drink; and he shall be filled with the holy Spirit, even from his mother's womb. Luke 1: 13-15
The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world. This is he of whom I said, After me cometh a man which is preferred before me: or he was before me. And I knew him not: but that he should be made manifest to Israel, therefore am I come baptizing with water. John 1:29-31 . . . . And looking upon Jesus as he walked, he saith, Behold the Lamb of God! John 1:36
John KNEW of Jesus from OT scripture as coming to be manifested to Israel as the Lamb of God but he did not KNOW him as in having previously MET him.