Luke 10:5

But it is said, Peace be to this house, that is, to them that dwell in the house. As if he says, I speak unto all, both the greater and the less, yet should not your salutation be addressed to them that are unworthy of it.

That in truth we should convey the message of peace, and that our very first entrance be attended with the blessing of peace.

(Hom. 35. in Matt.) Peace is the mother of all good things, without it all other things are vain. Our Lord therefore commanded His disciples on entering a house first to pronounce peace as a sign of good things, saying, Into whatever house ye enter, first say, Peace be to this house. (Hom. 32. in Matt. Orat. cont. Jud. 3.) And hence he who presides in the Church gives it, saying, Peace unto all. Now holy men ask for peace, not only that which dwells among men in mutual intercourse, but that which belongs to ourselves. For oftentimes we wage war in our hearts, and are disturbed even when no one troubles us; bad desires also frequently rise up against us. (ubi sup.) But lest any one should say, I am spending my own property in preparing a table for strangers, He first makes them offer the gift of peace, to which nothing is equal, that you may know that you receive greater things than you give.