John 6:17

Wherefore then doth Christ let them go, and not show Himself? And again, wherefore doth He show Himself walking alone upon the sea? By the first He teacheth them how great an evil it is to be forsaken by Him, and maketh their longing greater; by the second, again, He showeth forth His power. For as in His teaching they heard not all in common with the multitude, so in the case of the miracles they saw them not all with the mass of people, since it was needful that they who were about to receive in charge the presidency of the world, should have somewhat more than the rest.

Christ provideth for the good of his disciples not only when He is present in the body, but also when far away; for having abundance of means and of skill, He effecteth one and the same end by contrary actions. Observe, for instance, what He hath done here. He leaveth His disciples, and goeth up into a mountain; and they, when even was come, went down unto the sea. They waited for Him until evening, expecting that He would come unto them; but when even was come, they could no longer endure not to seek their Master; so great a love possessed them. They said not, "It is now evening, and night hath overtaken us, whither shall we depart? the place is dangerous, the time unsafe"; but, goaded by their longing, they entered into the ship. For it is not without a cause that the Evangelist hath declared the time also, but by it to show the warmth of their love.