John Calvin on John 1:34-35

34. I saw and testified. He means that what he declares is not doubtful; because God was pleased to make him fully and thoroughly acquainted with those things of which he was to be the witness to the world; and it is worthy of notice, that he testified that Christ was the Son of God, because he who gives the Holy Spirit must be the Christ, for to no other belongs the honor and the office of reconciling men to God.

John 1:35-39

35. The next day John was again standing, and two of his disciples; 36. And looking at Jesus walking, he said, Behold the Lamb of God! 37. And those two disciples heard him speak, and followed Jesus. 38. And Jesus turning, and looking at them following him, saith to them, What do you seek? And they said to him, Rabbi, (which, if you interpret it, is explained Master,) where dwellest thou? 39. He saith to them, Come and see. They came and saw where he dwelt, and remained with him that day; for it was about the tenth hour.