Mk 1:4 John did baptize in the wilderness, and preach the baptism of repentance for the remission of sins.
Mk 1:9 And it came to pass in those days, that Jesus came from Nazareth of Galilee, and was baptized of John in Jordan.
Mk 1:10 And straightway coming up out of the water, he saw the heavens opened, and the Spirit like a dove descending upon him:
Mk 1:11 And there came a voice from heaven, saying, Thou art my beloved Son, in whom I am well pleased.
Why did our Lord, the sinless one, choose to be baptised? He did not need to repent. He had no sins which needed remission. He was holy from birth.
He chose to be baptised to humble Himself and show his submission to the Father. Who was well pleased.
Throughout the New Testament there are stories of adults finding the Lord and being baptised. Nowhere is this act described as a replacement for circumcision. (Correct me if I am wrong, Please). Certainly our Lord did not say so. There is a tenuous argument for infant baptism when whole housholds are baptised, but no real proof that this occurred.
The evidence is that baptism is to be a public act of faith, contrition, submission, and repentence. This act is undertaken by a person old enough to understand what it means.
While infant baptism does no harm, I believe, based on the Bible, that it does no real good.