John 1:31

I knew him not. As if with the emphasis, “Even I did not know him” to be the Messiah. John’s early witness on behalf of the Messiah was based on direct revelation. There had been no collusion between Jesus and John. Knowing of the circumstances attending the early years of Jesus’ life and of His perfection of character, John believed Jesus to be the Promised One, but until the baptism he had no positive evidence that this was so (see DA 109).

Manifest to Israel. John was the “voice” from God (see on v. 23) directing men to “the Lamb of God” (see on v. 29). The baptism of Jesus marked the climax of John’s mission, though his labors continued for perhaps a year and a half more. He declared, after the baptism, that Jesus “must increase,” and he himself “decrease” (eh. 3:30).