Adam Clarke on Matthew 15:28

O woman, great is thy faith - The hinderances thrown in this woman's way only tended to increase her faith. Her faith resembles a river, which becomes enlarged by the dykes opposed to it, till at last it sweeps them entirely away with it.

Her daughter was made whole - Persevering faith and prayer are next to omnipotent. No person can thus pray and believe, without receiving all his soul requires. This is one of the finest lessons in the book of God for a penitent, or for a discouraged believer. Look to Jesus! As sure as God is in heaven, so surely will he hear and answer thee to the eternal salvation of thy soul! Be not discouraged at a little delay: when thou art properly prepared to receive the blessing, then thou shalt have it. Look up; thy salvation is at hand. Jesus admires this faith, to the end that we may admire and imitate it, and may reap the same fruits and advantages from it.