"Jesus was not a sinner.
He did not need to, be baptized, except that 
He might, be an example to those who would believe on His name, and that He thus might be able vicariously to impart baptism to those who were unable to be baptized after they had believed.
*The thief on the cross fell into this class of those who are in need of a vicarious impartation of baptism.
In any discussion of the question of baptism for the dead, John 3:5 will come up for consideration. This verse reads: "Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God."
The Mormons believe in the impartation of baptism vicariously, seeing that they apply 1 Corinthians 15:29 (Otherwise, what do people mean by being baptized on behalf of the dead? If the dead are not raised at all, why are people baptized on their behalf? ) as they do.
---But their argument is faulty.
After a man is dead, it is impossible for him to hope for the truth. Isaiah 38:18 records this: "For the grave cannot praise Thee, death cannot celebrate Thee: they that go down into the pit cannot hope for Thy truth." Thus, vicarious baptism, performed in an attempt to impart it to a man after he has died, would do no good.
The dying thief was one who had no such opportunity to walk in the "works, which God hath before ordained," wherein a believer should walk. (See Eph. 2:10, Newberry's version.) Thus the thief had to accept Jesus' baptism without himself being baptized. The baptism was imputed to the thief, and the verse in John 3:5 was thus fulfilled for the thief."
Paul O. Campbell/1939