The Didache opens with the Two Ways, a stark ethical framework, "there are two ways, one of life and one of death, and there is a great difference between the two ways," that lays out the way of life through a dense sequence of moral instruction closely echoing the Sermon on the Mount and the way of death through a long list of vices to avoid, material scholars believe drew on an older Jewish ethical teaching document also reflected in the roughly contemporary Epistle of Barnabas.
The text then turns practical, giving what may be Christianity's earliest surviving instructions on baptism, preferring immersion in "living water," meaning naturally running water, but explicitly permitting pouring water over the head three times if sufficient water for immersion cannot be found, a flexible, pastorally realistic provision; on fasting, prescribing Wednesdays and Fridays specifically to distinguish Christian practice from the Monday and Thursday fasts of "the hypocrites," a barely veiled reference to Pharisaic Jewish practice; and on the Eucharist, preserving prayers of thanksgiving over the cup and the bread that are among the oldest eucharistic prayer texts to survive outside the New Testament itself. Later chapters address how a young, still loosely organized church should evaluate traveling apostles and prophets, warning against those who overstay their welcome or ask for money, and the whole text closes with a short, urgent warning about deceivers appearing before the world's end.