Theophylact of Ohrid

"Into whatever house you enter," He says, "first say: peace be to this house," that is, greet those who are in the house; then, showing that this is not merely a greeting but also a blessing, He says: if the householder is worthy, then he will be blessed, and if he is an offender and incapable of receiving peace, if he is an enemy and opponent of your word and teaching, then the blessing will not come to him, but "will return to you."

Commentary on Luke ↗

Titus of Bostra

Hence it is added, And if the son of peace be there, your peace shall rest upon it. As if he says, You indeed shall utter the word, but the blessing of peace shall be applied wherever I shall deem men worthy of it. But if any one is not worthy, ye are not mocked, the grace of your word has not perished, but is returned unto you. And this is what is added, But if not, it shall return unto you again.

Catena Aurea by Aquinas ↗

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 ↗

Bonaventure

And because they might fear that they would offer peace in vain, therefore he adds: And if a son of peace be there: of peace according to eternal foreknowledge, of whom it is said in John 11 that "Jesus suffered, that he might gather together the children of God who were scattered"; of whom it is said in 2 Timothy 2: "The Lord knows who are his." Such are sons of peace, because it is said in Matthew 5: "Blessed are the peacemakers, for they shall be called children of God." — In such a one the word of preaching has efficacy: on …

Commentary on Luke, Chapter 10 ↗