John Chrysostom

But Christ saith, "I am not sent, but unto the lost sheep of the house of Israel." What then did the woman, after she heard this? Was she silent, and did she desist? or did she relax her earnestness? By no means, but she was the more instant. But it is not so with us; rather, when we fail to obtain, we desist; whereas it ought to make us the more urgent. And yet, who would not have been driven to perplexity by the word which was then spoken? Why His silence were enough to drive her to despair, but His answer did so very much more. …

Homily on the Gospel of Matthew 52 ↗

Augustine of Hippo

A question arises here on that point: How is it that we have come from the Gentiles to the sheepfold of Christ if he was sent only to the lost sheep of the house of Israel? What is the meaning of this puzzling dispensation? The Lord knew why he came—certainly to have a church among all the Gentiles—and he yet said that he was sent only to the lost sheep of the house of Israel? …

Sermon 77.2 ↗

Jerome

He did not answer him a word. Not out of Pharisaic pride, nor out of the scorn of the Scribes; but so that he would not seem to be contrary to his own command, by which he had instructed: Do not go into the way of the Gentiles, and do not enter into the cities of the Samaritans (Luke 10:5). For he did not wish to give occasion to the accusers and reserved the perfect salvation of the Gentiles for the time of his passion and resurrection. …

Commentary on Matthew ↗

Hilary of Poitiers

The Lord remains patiently silent, reserving the privilege of salvation for Israel. And the pitying disciples join in a plea. But he, holding in his hands the secret of his Father's will, answers that he was sent to the lost sheep of Israel. It thus became absolutely clear that the daughter of the Canaanite woman represented a type of the church when the woman kept asking for what was bestowed upon the others. …

Commentary on Matthew 15.4 ↗