I don't think John 1:26-33 demonstrate that John did not know, rather, it is him saying his audience did not know. John's mother and father knew before John and Jesus were even born- and when John saw Jesus coming to him he recognized Jesus as the Lamb right away...
I believe the account in John occurred after Jesus' actual baptism. (Matthew 3:13-17) John the Baptist makes the comment that he did not know Jesus was the messiah in both verses 31 and 33. I find the following commentary compelling as to why John would have made those statements:
John 1:33,34
And I knew him not: but he that sent me to baptize with water, the same said unto me, Upon whom thou shalt see the Spirit descending, and remaining on him, the same is he which baptizeth with the Holy Ghost.
[The same said ...] This was the sign by which he was to know the Messiah. He was to see the Spirit descending like a dove and abiding on him. It does not follow, however, that he had no intimation before this that Jesus was the Christ, but it means that by this he should know it infallibly. From Matt 3:13-14, it seems that John supposed, before the baptism of Jesus, that he CLAIMED to be the Messiah, and, that he believed it; but the infallible, certain testimony in the case was the descent of the Holy Spirit on him at his baptism.
[That this is the Son of God] This was distinctly declared by a voice from heaven at his baptism, Matt 3:17. This John heard, and he testified that he had heard it.
(from Barnes' Notes, Electronic Database Copyright © 1997, 2003, 2005, 2006 by Biblesoft, Inc. All rights reserved.)
...I agree that John didn't baptize in Jesus' name; that much is clear to me. What has not been clear to me is whether or not Jesus' disciples baptized in Jesus' name during his ministry. His disciples were at least casting out demons in his name. It just seems strange to me that they would not baptize in his name- they were baptizing... was it just the same as John's baptism? And if it was the same- why did this happen?
...
John's baptism was begun to prepare Jewish people for the coming of Jesus; the NT church was not yet founded. The Old Testament sacrificial system was still in force for remitting sin. John's baptism pointed to the future Christian baptism that would rely upon Jesus' sacrifice to remit sin. See Acts 2:38 and Romans 6:4-6.
Also, as seen in Acts 19:1-6 Paul rebaptized people in the name of the Lord Jesus.
...
Then a debate arose among the disciples of John with a certain Jew about purification. And they came to John and said to him, “Rabbi, He who was with you beyond the Jordan, to whom you have borne witness, behold He baptizes, and all are coming to Him.”
Now, I know a lot of people insist on the KJ, but I think the Berean literal translation gives context that makes a lot more sense to me. John (the author of the Gospel- not "the baptist") is refering to himself (admittedly a speculation, but a sensible one- John refers to himself in the third person more than once.) when he says "a certain Jew". That's why the next verse is talking about Jesus' ministry- because the Baptist's disciples were arguing with John about how to baptize...
I have to disagree since verses 27-30 show that it is John the Baptist speaking. The exchange would seem to emphasize that who was administering water baptism was of no particular significance.(verse 27)
Also relevant is Jesus was present during baptisms but did not water baptize anyone Himself. (John 4:1-2)
John 3:23-30
23 And John also was baptizing in Aenon near to Salim, because there was much water there: and they came, and were baptized.
24 For John was not yet cast into prison.
25 Then there arose a question between some of John's disciples and the Jews about purifying.
26 And they came unto John, and said unto him, Rabbi, he that was with thee beyond Jordan, to whom thou barest witness, behold, the same baptizeth, and all men come to him.
27
John answered and said, A man can receive nothing, except it be given him from heaven.
28 Ye yourselves bear me witness, that I said, I am not the Christ, but that I am sent before him.
29 He that hath the bride is the bridegroom: but the friend of the bridegroom, which standeth and heareth him, rejoiceth greatly because of the bridegroom's voice: this my joy therefore is fulfilled.
30
He must increase, but I must decrease.
KJV
...Indeed, Luke 24 says
And said unto them, Thus it is written, and thus it behoved Christ to suffer, and to rise from the dead the third day: And that repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem.
But I don't think it means that it repentance and remission of sins were preached in his name for the first time in Jerusalem. I think Jesus is telling his disciples how they are going to proceed- preach to all nations, beginning at Jerusalem- and that will fulfill what was written (the "word of the lord going out from Jerusalem"-which does not necessarily mean it originated there for the first time).
Notice Jesus makes mention of His death, burial and resurrection and goes on to say that repentance and remission of sins would be preached in His name beginning at Jerusalem. It is on the condition of Jesus sacrifice that sins are remitted through water baptism in His name. (Acts 2:38, 22:16) Also it is in water baptism that a person is buried with Jesus into His death according to Romans 6:4-6:
Rom 6:4-6
"Therefore
we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
5
For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection:
6 Knowing this, that
our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin."