Theophylact of Ohrid — as excerpted in the Catena Aurea on Mark 6:45-52

“Now the Lord permitted His disciples to be in danger, that they might learn patience; wherefore He did not immediately come to their aid, but allowed them to remain in danger all night, that He might teach them to wait patiently, and not to hope at once for help in tribulations. For there follows, And he saw them toiling in rowing, for the wind was contrary unto them: and about the fourth watch of the night, he cometh unto them walking upon the sea.”