12 But you are unworthy. Become worthy by your assiduity. For that it both is possible that the unworthy should become worthy from his assiduity; and that God assents more when called on by ourselves than by others; and that he often delays the giving, not from the wish that we should be utterly perplexed, nor to send us out with empty hands; but in order that he may become the author of greater good things to us— these three points I will endeavour to make evident by the parable which has today been read to you.
The woman of Chanaan had come to Christ praying on behalf of a daughter possessed by a demon, and crying out with much earnestness (it says, “Have pity on me, Lord, my daughter is badly possessed by a demon.”) See, the woman of a strange nation, and a barbarian, and outside of the Jewish commonwealth. For indeed what else (was she) than a dog, and unworthy of the receiving her request? For “it is not,” he says, “good to take the children's bread, and to give it to the dogs.”
But, all the same, from her assiduity, she became worthy. For not only did he admit her into the nobility of children, dog as she was; but also he sent her off with that high encomium saying, “O woman great is your faith; be it done to you as you will.” Now when the Christ says, “great is your faith,” seek thou no other demonstration of the greatness of soul which was in the woman. Do you see how, from her assiduity the woman, being unworthy, became worthy? Desirest thou also to learn that we accomplish (our wish) by calling on him by ourselves more than by others?
She cried out, and the disciples having come to him say, “Let her go away, for she is crying after us:” and to them he says, “I am not sent, unless to the lost sheep of the house of Israel.” But when she had come to him by herself and continued crying, and saying, “Yes, Lord, for even the dogs eat from the table of their masters,” then he granted the favour and says, “Be it done unto you as you will.” Do you see how, when they were entreating him, he repelled; but when she who needed the gift herself cried out, he assented?
For to them he says, “I am not sent, unless to the lost sheep of the house of Israel;” but to her he said, “Great is your faith; be it done unto you as you will.” Again, at the beginning and in the prelude of her request he answered nothing; but when both once and twice and thrice she had come to him, then he granted the boon; by the issue making us believe that he had delayed the giving, not that he might repel her but that he might display to us all the woman's endurance. For if he had delayed in order that he might repel her, he would have not granted it even at the end; but since he was waiting to display to all her spiritual wisdom, on this account he was silent. For if he had granted it immediately and at the beginning, we should not have known the woman's virtue. “Let her go” it says, “because she is clamouring behind us.”
But what (says) the Christ? You hear a voice, but I see the mind: I know what she is going to say. I choose not to permit the treasure hidden in her mind to escape notice; but I am waiting and keeping silence; in order that having discovered it I may lay it down in publicity, and make it manifest to all.
Source: Homily Concerning "Lowliness of Mind" (New Advent)