Be not forgetful to entertain strangers: for thereby some have entertained angels unawares. (Heb. 13:2)
Accepting the task of hospitality, the patriarch [Abraham] used to sit at the entrance to his tent (cf. Gen. 18:1), inviting all who passed by, and his table was laden for all comers including the impious and barbarians, without distinction. Hence he was found worthy of that wonderful banquet when he received angels and the Master of all as guests. We too, then, should actively and eagerly cultivate hospitality, so that we may receive not only angels, but also God Himself. "For inasmuch," says the Lord, "as you have done it to one of the least of these My brethren, you have done it unto Me" (Matt. 25:40). It is good to be generous to all, especially to those who cannot repay you.
...Even if you have only bread or water, with these you can still meet the dues of hospitality. Even if you do not have these, but simply make the stranger welcome and offer him a word of encouragement, you will not be failing in hospitality. Think of the widow mentioned in the Gospel by our Lord: with two mites she surpassed the generous gifts of the wealthy.
-- St. Theodoros, the Great Ascetic