From the Holy Gospel according to St. Matthew (14:22-34)

At that time, Jesus made his disciples get into the boat and go before him to the other side, while he dismissed the crowds. And after he had dismissed the crowds, he went up on the mountain by himself to pray. When evening came, he was there alone, but the boat was in the middle of the sea, beaten by the waves; for the wind was against it. And in the fourth watch of the night Jesus came to them, walking on the sea. But when the disciples saw him walking on the sea, they were terrified, saying, "It is a spirit!" And they cried out for fear. But immediately Jesus spoke to them, saying, "Take heart, it is I; have no fear."

And Peter answered him, saying, "Lord, if it is you, bid me come to you on the water." Jesus said, "Come." So Peter got out of the boat and walked on the water and came to Jesus; but when he saw the mighty wind, he was afraid, and beginning to sink he cried out, "Lord, save me." Jesus immediately reached out his hand and caught him, saying to him, "O man of little faith, why did you doubt?" And when they got into the boat, the wind became calm. And those in the boat came and worshiped Jesus, saying, "Truly you are the Son of God." And when they had crossed over, they came to land at Gennesaret.