John Chrysostom — as excerpted in the Catena Aurea on John 6:1-14

“(Hom. xlii. 3) Observe the difference between the servant and the lord. The Prophets received grace, as it were, by measure, and according to that measure performed their miracles: whereas Christ, working this by His own absolute power, produces a kind of superabundant result. When they were filled, He said unto His disciples, Gather up the fragments that remain, that nothing be lost. Therefore they gathered them together, and filled twelve baskets with the fragments. This was not done for needless ostentation, but to prevent men from thinking the whole a delusion; which was the reason why He made use of an existing material to work from. But why did He give the fragments to His disciples to carry away, and not to the multitude? Because the disciples were to be the teachers of the world, and therefore it was most important that the truth should be impressed upon them. Wherefore I admire not only the multitude of the loaves which were made, but the definite quantity of the fragments; neither more nor less than twelve baskets full, and corresponding to the number of the twelve Apostles.”