Gregory the Dialogist

And if the son of peace be there, your peace shall rest upon him; but if not, it shall return to you. The peace which is offered from the mouth of the preacher either rests in the house, if there be a son of peace in it, or returns to the same preacher; because either someone will be predestined to life, and follows the heavenly word which he hears; or if no one shall have been willing to hear, the preacher himself will not be without fruit, because peace returns to him, since a reward is recompensed to him from the Lord for the …

Forty Gospel Homilies, Homily 17 ↗

Thomas Aquinas

Then he continues with the effect both on the good and on the wicked. And if the house is worthy... We can say that such a house will obtain a blessing. Hence the apostles or bishops in first turning toward the people say, "Peace be to you." So it says in Numbers (6:27): "They shall invoke my name upon the people of Israel, and I shall bless them." But if it is not worthy, your peace will return to you. Why does he say this? Did he not say that they should first inquire? …

Commentary on Matthew ↗

Remigius of Rheims

Thus either the hearer, being predestined to eternal life, will follow the heavenly word when he hears it; or if there be none who will hear it, the preacher himself shall not be without fruit; for his peace returns to him when he receives of the Lord recompense for all his labour.

Catena Aurea by Aquinas ↗