13 And Peter again afterwards, when he had overcome Simon, in sowing the doctrine of God among the people, and in teaching chastity, stirred up the minds of the Gentiles. And when these sought him, the Christians begged that he would withdraw himself for a little while. And although he was desirous to suffer, yet was he moved at the sight of the people praying, for they asked him to save himself for the instruction and strengthening of his people. Need I say more? At night he begins to leave the town, and seeing Christ coming to meet him at the gate, and entering the city, says: Lord, where are You going?
Christ answers: I am coming to be crucified again. Peter understood the divine answer to refer to his own cross, for Christ could not be crucified a second time, for He had put off the flesh by the passion of the death which He had undergone; since: “In that He died, He died unto sin once, but in that He lives, He lives unto God.” So Peter understood that Christ was to be crucified again in the person of His servant. Therefore he willingly returned; and when the Christians questioned him, told them the reason. He was immediately seized, and glorified the Lord Jesus by his cross.
Source: Sermon against Auxentius (New Advent)