Blessed Theophylact on Matthew 15:21-28

Now Jesus shows the reason why He put off healing her at the beginning. So that the faith and understanding of the woman might be made manifest, Christ did not immediately give His ascent and even drove her away. But now when her faith has been revealed she hears the words of praise, “Great is thy faith.”

From Blessed Theophylact, The Explanation of the Holy Gospel According to St. Matthew, Chrysostom Press, 2008