John Chrysostom
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.
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.
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.
Now mark the excellence of the Apostles. They are bid to utter nothing relating to sensible things, such as Moses and the Prophets spoke of, namely, earthly goods, but certain new and marvellous things, namely, the kingdom of God.