Then Jesus called his disciples unto him, and said, I have compassion on the multitude, because they continue with me now three days, and have nothing to eat: and I will not send them away fasting, lest they faint in the way. And his disciples say unto him, Whence should we have so much bread in the wilderness, as to fill so great a multitude? (Matthew 15:32,33)
Frankly, this seems like just a rerun of the feeding of the five thousand. It appears to be a repetition, and we wonder why Matthew included it since it doesn't seem to add any further advancement of the messianic claims of the Lord Jesus. However, this is a section in which the emphasis is not upon Jesus pressing His messianic claim but the emphasis is on the rejection of His claim. And this miracle shows how slowly the disciples were to learn. They had already witnessed the feeding of the five thousand (and I think it took place only a few days before this), yet here they raise the same old objections of unbelief. Again His disciples say to Him, "Whence should we have so much bread in the wilderness, as to fill so great a multitude?"
And Jesus saith unto them, How many loaves have ye? And they said, Seven, and a few little fishes. And he commanded the multitude to sit down on the ground. And he took the seven loaves and the fishes, and gave thanks, and brake them, and gave to his disciples, and the disciples to the multitude. (Matthew 15:34-36)
This is a revelation that the disciples had not really learned the lesson. Their reluctance to believe actually constitutes a form of rejection. My friend, unbelief is sin. In Romans 14:23 it says "whatsoever is not of faith is sin." In Hebrews 12:1 we are admonished to "lay aside every weight, and the sin which doth so easily beset us." What is that weight? I think it is unbelief. Unbelief is sin. I am willing to make this confession: I wish that I believed Him more. He is worthy to be believed; I ought to believe Him fully, but the problem is with me. And I suspect that the problem is with you, also. This chapter reveals that our Lord's disciples are not keeping up. They are slow to believe and slow to understand. This is actually hindering the Lord Jesus. It seems at this point that, since He has reached the breaking point with the religious rulers, He is having a real problem with His disciples. He appears to be just marking time until they catch up. Frankly, He is very patient with you and me, also. Many of us need to catch up; we are far behind in our belief and understanding. Oh, that we might believe Him!
—From Edited Messages on Matthew by J. Vernon McGee