“This fast,” he said, “is very good, if you keep the commandments of the Lord. So observe this fast which you are going to keep in this way: First of all, guard against every evil word and every evil desire, and cleanse your heart of all the vanities of this world. If you observe these things, this fast will be complete. And here is what you will do: when you have finished the above-mentioned, on that day when you are fasting, you will taste nothing except bread and water, and you will be aware of the amount of the cost of your food you would have eaten on that day which you are going to keep. Having set it aside, you will give it to a widow or an orphan or someone else in need, and in this way you will be humble minded, so that from your humility the one who receives may fill his soul and pray to the Lord for you.
If, then, you complete the fast in this way, as I command you, our sacrifice will be acceptable before God [cf. Phil. 4:18; Isa. 56:7; 1 Pet. 2:5], and this fast will be recorded, and the service done in this way is good and joyous and acceptable to the Lord. This is the way you shall observe these things, with your children and all your house; if you observe them, you will be blessed and as many as hear them and keep them will be blessed, and whatever they ask from the Lord they will receive.”
(Shepherd of Hermas, The Apostolic Fathers, p. 213)