Now concerning baptism, baptize as follows: after you have reviewed all these things, baptize in the name of the Father and of the Son and of the Holy Spirit in running water. But if you have no running water, then baptize in some other water; and if you are not able to baptize in cold water, then do so in warm. But if you have neither, then pour water on the head three times in the name of the Father and Son and Holy Spirit. And before the baptism let the one baptizing and the who who is to be baptized fast, as well as any others who are able. Also, you must instruct the one who is to be baptized to fast for one or two days beforehand.
Didache, ch. 7 (early 2nd century) trans. Michael W. Holmes, The Apostolic Fathers: Greek Texts and English Translations, 3rd edn (Grand Rapids: Baker, 2007).