And there were set there six waterpots of stone, after the manner of the purifying of the Jews, containing two or three firkins apiece. After the manner of the purifying of the Jews - Or, for the purpose of the purifying of the Jews. The preposition κατα, which I have translated, for the purpose, often denotes in the best Greek writers the final cause of a thing. See several examples produced by Raphelius, from Arrian and Herodotus. These six vessels were set in a convenient place, for the purpose of the Jews washing their hands before they sat down to meat, and probably for other purposes of purification. See this custom referred to in Matthew 15:2 (note). As to the number six, we need seek for no mystery in it; the number of pots was proportioned to the number of the guests.
Containing two or three firkins apiece - Measures or metretes, μετρητας. Bishop Cumberland supposes that the Syrian metretes is here meant, which he computes to have held seven pints and one eighth of a pint; and, if this computation be right, the whole six water pots might have contained about fourteen gallons and a quart. Others make each metretes to contain ten gallons and two pints: see Arbuthnot. But the contents of the measures of the ancients are so very uncertain that it is best, in this and numberless other cases, to attempt to determine nothing.