The Didache, Didache 7
Concerning baptism, baptize in this way: after you have said all these things, baptize into the name of the Father, the Son, and the Holy Spirit using living water. If you do not have living water, use other water; if you cannot baptize in cold water, use warm water. If you have neither, pour water on the head three times into the name of the Father, the Son, and the Holy Spirit. Before the baptism, let the one who baptizes and the one who is baptized fast, and anyone else who is able; you must command the one being baptized to fast for one or two days.
Greek
Περὶ δὲ τοῦ βαπτίσματος, οὕτω βαπτίσατε: ταῦτα πάντα προειπόντες, βαπτίσατε εἰς τὸ ὄνομα τοῦ πατρὸς καὶ τοῦ υἱοῦ καὶ τοῦ ἁγίου πνεύματος ἐν ὕδατι ζῶντι. ἐὰν δὲ μὴ ἔχῃς ὕδωρ ζῶν, εἰς ἄλλο ὕδωρ βάπτισον: εἰ δ’ οὐ δύνασαι ἐν ψυχρῷ, ἐν θερμῷ. ἐὰν δὲ ἀμφότερα μὴ ἔχῃς, ἔκχεον εἰς τὴν κεφαλὴν τρὶς ὕδωρ εἰς ὄνομα πατρὸς καὶ υἱοῦ καὶ ἁγίου πνεύματος. πρὸ δὲ τοῦ βαπτίσματος προνηστευσάτω ὁ βαπτίζων καὶ ὁ βαπτιζόμενος καὶ εἴ τινες ἄλλοι δύνανται: κελεύεις δὲ νηστεῦσαι τὸν βαπτιζόμενον πρὸ μιᾶς ἢ δύο.