Matthew 14:27

But straightway Jesus spake unto them, saying, Be of good cheer; it is I; be not afraid.

Almost the entire night Jesus had spent in prayer, almost the entire night had His disciples struggled to reach the opposite shore. It was in the fourth and last watch of the night, between three and six in the morning, when the extreme darkness was dissolving into a gray dawn, that Jesus went out to them, walking along over the sea, on the water, as the evangelist says twice. The disciples, who were given to superstition, as were most of the Jews, were filled with the most extravagant fear, the dread of phantoms, ghosts, or spirits being very strong. They screamed for fear. But the calm voice of Jesus assures them. Thus the believers, as Luther says, in the midst of their tribulation, do not believe that God is God, but think He is a ghost come to frighten them and to destroy them, surrounded, as they are, by their troubles. But He will always prove to be the gracious and merciful Lord.