Albert Barnes on John 2:6

Six water-pots of stone. Made of stone; or, as we should say, stoneware.

After the manner. After the usual custom.

Of the purifying. Of the washings or ablutions of the Jews. They were for the purpose of washing the hands before and after eating (Mt 15:2), and for the formal washing of vessels, and even articles of furniture, Lk 11:39, Mk 7:3,4.

Two or three firkins. It is not quite certain what is meant here by the word firkins. It is probable that the measure intended is the Hebrew bath, containing about 7 gallons.