Albert Barnes on Matthew 10:13

If the house be worthy. That is, if the family be worthy, or be willing to receive you as my disciples.

Let your peace come upon it. That is, let the peace or happiness which you seek, or for which you pray, in saluting it, Lu 10:5 come upon it; or seek their peace and happiness by prayer, instruction, by remaining with them, and imparting to them the blessings of the gospel.

But if it be not worthy, etc. If the family be unwilling to receive you; if they show themselves unfriendly to you and your message, let your peace return to you. This is a Hebrew mode of saying that your peace should not come upon it, Ps 35:13. It is a mode of speaking derived from bestowing a gift. If people were willing to receive it, they derived the benefit from it; if not, then of course the present came back, or remained in the hand of the giver. So Christ figuratively speaks of the peace which their labour would confer. If received kindly and hospitably by the people, they would confer on them most valuable blessings. If rejected and persecuted, the blessings which they sought for others would come upon themselves. They would reap the benefit of being cast out and persecuted for their Master's sake, Mt 5:10.

(c) "return to you" Ps 35:13