John 1:29-34

The next day John seeth Jesus. Here Jesus first appears, in person, in John's account, who omits all the details given by Matthew and Luke of his earlier life. He was now thirty years old, and came from Galilee to Jordan to be baptized of John. This interview was after the baptism (Joh 1:33), and probably after the Temptation.

Behold the Lamb of God. Innocent like the lamb, to be offered as a lamb, "led as a lamb to the slaughter" (Isa 53:7). The lamb was commonly used as a sin offering (Le 4:32), and when John points to Jesus as "the" Lamb of God he can only mean that God had provided him as a sacrificial offering.

The sin of the world. Not of Jews only, but of Gentiles. John points to Jesus as the world's Savior.
This is he of whom I said. See Joh 1:27.

He was before me. Existed before I was born.
I knew him not. Knew not that God had chosen him to be the Christ. He knew, however, that he should be manifested in some way through his baptism. I saw the Spirit descending from heaven like a dove. See Mt 3:16, and notes. It was revealed to John that the Christ would thus be revealed. Indeed it was the anointing of the Spirit that made Jesus the Anointed, the Christ.
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