And his disciples say unto him, Whence should we have so much bread in the wilderness, as to fill so great a multitude?

People's New Testament

15:33 Whence should we get so much bread? This was not said in ignorance of the Lord's creative power, but probably to suggest the need of its exercise. They could not have forgotten the events narrated in Mt 14:15-21.

Matthew Henry's Concise Commentary

15:29-39 Whatever our case is, the only way to find ease and relief, is to lay it at Christ's feet, to submit it to him, and refer it to his disposal. Those who would have spiritual healing from Christ, must be ruled as he pleases. See what work sin has made; what various diseases human bodies are subject to. Here were such diseases as fancy could neither guess the cause nor the cure of, yet these were subject to the command of Christ. The spiritual cures that Christ works are wonderful. When blind souls are made to see by faith, the dumb to speak in prayer, the maimed and the lame to walk in holy obedience, it is to be wondered at. His power was also shown to the multitude, in the plentiful provision he made for them: the manner is much the same as before. All did eat, and were filled. Those whom Christ feeds, he fills. With Christ there is bread enough, and to spare; supplies of grace for more than seek it, and for those that seek for more. Christ sent away the people. Though he had fed them twice, they must not look for miracles to find their daily bread. Let them go home to their callings and their own tables. Lord, increase our faith, and pardon our unbelief, teaching us to live upon thy fulness and bounty, for all things pertaining to this life, and that which is to come.