gallon
From LSJ
ἐάν μή διδάξητε περί ἀρετὴς τούς τό ἀργύριον κλέψαντας, οὐ ταξόμεθα οἱ ὁπλῖται → if you don't teach those who have stolen money a lesson on moral virtue, we, the hoplites, will not line up
Use Ar. and P. χοῦς, ὁ (about three-quarters of a gallon).