Charles Spurgeon Commentary Luke 10:5-6

"And into whatsoever house ye shall enter, first say, Peace [be] to this house. And if a son of peace be there, your peace shall rest upon him: but if not, it shall turn to you again." — Luke 10:5-6 (ASV)

So that it will not be wasted. Wish well, and your well-wishing will do you good, even if it does nobody else good. Our chickens come home to roost. If they are curses, they will come upon us; if they are blessings, they will bless us as well as others.