Some people teach that you must be of age to be able to repent before you can be baptized. I strongly disagree with this statement for one:
1. First you have to be living in sin for a need to repent.
2. No words have to be spoken to repent.
3. What does it mean to repent?
--to feel sorry, self-reproachful, or contrite for past conduct; regret or be conscience-stricken about a past action, attitude, etc.
--to feel such sorrow for sin or fault as to be disposed to change one's life for the better; be penitent.
4. Babies need to be saved just as adults therefore, it is a bad practice to withhold baptism from children. They need to be prepared for the kingdom as well.
What did Jesus say about repentance?
But go ye and learn what that meaneth, I will have mercy, and not sacrifice: for I am not come to call the righteous, but sinners to repentance.
Even the righteous have to be baptized in Jesus name and filled with the Holy Ghost -- without the need to repent.
When Jesus heard it, he saith unto them, They that are whole have no need of the physician, but they that are sick: I came not to call the righteous, but sinners to repentance.
To repent is an internal emotion -- it could be spoken aloud but that is not required.
Babies have not sinned and therefore, they have no need to repent.
To enter God's kingdom everyone MUST be baptized in Jesus name and filled with the Holy Ghost.
DO NOT WITHHOLD BAPTISM FROM ANYONE - INCLUDING BABIES / CHILDREN
Lastly, I think most people do repent automatically regarding past sins as they hear the word of God leading up to their baptism.