Told more than once
Peter's confession
The hinge of the Synoptic Gospels: the question of who Jesus is, answered aloud, and immediately followed by the first prediction of the passion.
What the accounts share
Mark 8:27-30 and Luke 9:18-21
Jesus asks who men say that he is, then who the disciples say, and Peter answers. Both follow it with a charge to tell no one.
The accounts
Mark 8:27-30
27And Jesus went forth and his Disciples into the towns of Cæsarea-Philippi; and in the way he asked his Disciples, saying to them: Whom do men say that I am? 28Who answered him, saying: John the Baptist, some Elias, & other some as it were one of the Prophets. 29Then he saith to them: But whom do you say that I am? Peter answering said to him: Thou art Christ. 30And he threatened them that they should not tell any man of him.
Luke 9:18-21
18And it came to pass; when he was alone praying, his Disciples also were with him; and he asked them saying: Whom do the multitudes say that I am? 19But they answered, and said: John the Baptist; and some, Elias; but some, that one of the Prophets before time, is risen. 20And he said to them: But whom say ye that I am? Simon Peter answering, said: The Christ of God. 21But he rebuking them, commanded that they should tell this to no man,
Douay-Rheims. Other translations are linked rather than reproduced.