John 2:6 - Coke's Commentary on the Holy Bible

After the manner of the purifying of the Jews,— Besides the purifications appointed by the law of God, there were a multitude of others then practised, in compliance with the tradition of the elders. Possibly this clause is thrown in by St. John, by way of explanation, as he wrote this gospel for the use of the Gentiles, who might be strangers to the Jewish customs. These water-pots are said to contain two or three firkins a-piece. Now the measures of the ancients are so very uncertain, that it is hardly possible to determine the exact contents of these vessels: some have computed them to contain about two or three hogsheads; and the Greek is so rendered in our translation, as to make them contain above one hundred gallons; but it is hardly probable the vessels were so large; and as the original word μετρητας signifies no more than measures, it is much better that we should leave it as we find it, unless the quantity could be determined with more certainty. It seems most probable that as the Jewish bath was the most common measure used in liquids, this is the quantity designed, where measuresare expressed without any limitation; and as the Jewish bath is reckoned to contain four gallons and a half, the contents of these vessels, if they are computed only at two measures each, will amount to no less than fifty-four gallons.