He didn't READ it somewhere. He HEARD it.
Aguest,
This assumes that Peter was there at that Baptism. Where is your proof? We know that John the Baptist was there and what did John or anyone else that was present hear? Matt 3:17 And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased. Or in John we learn: John 1:33 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. 34 And I saw, and bare record that this is the Son of God. Peter heard nothing at this baptism. I know since it was not a direct revelation from the Father in heaven as you teach. Our Lord's words to Peter meant something else. How do I know this. Because John in this same chapter of this Gospel revealed it like this: 1:40 One of the two who heard John speak and followed Jesus was Andrew, Simon Peter’s brother. 41 He first found his own brother Simon and said to him, “We have found the Messiah” (which means Christ). That is the truth and John recorded it for us. Then what did Jesus mean when he said "flesh and blood hath not revealed it unto thee, but my Father which is in heaven." We know that it was Andrew a man of flesh and blood, but our Lord took this further and taught that it was not Andrew that caused Peter to come to this conclusion. Peter came to this conclusion another way. After all our Lord referred to the words in scripture as being from the Father and they do speak to us all even today. In that case Peter heard it the way John the Baptiser heard his message from the Father who is in heaven that was responsible for such texts. We know this since Jesus said about such writings: Joh 5:47 But if you do not believe his writings, how will you believe my words?” Or Paul who said: Ro 16:26 but has now been disclosed and through the prophetic writings has been made known to all nations, according to the command of the eternal God, to bring about the obedience of faith— 2Ti 3:15 and how from childhood you have been acquainted with the sacred writings, which are able to make you wise for salvation through faith in Christ Jesus. This is Jewish terminology, the way they thought and spoke. I cannot believe what you are saying about Peter. I believe what Jesus taught about scripture and the way Jesus understood Peter came this conclusion.
Joseph