John 2:7

With water - This was done by the servants employed at the feast. It was done by “them,” so that there might be no opportunity of saying that the disciples of Jesus had filled them with wine to produce the “appearance” of a miracle. In this case there could be no deception. The quantity was very considerable. The servants would know whether the “wine” or “water” had been put in these vessels. It could not be believed that they had either the power or the disposition to impose on others in this manner, and the way was therefore clear for the proof that Jesus had really changed what was known to be water into wine.

To the brim - To the top. So full that no wine could be poured in to give the appearance of a mixture. Further, vessels were used for this miracle in which wine had not been kept. These pots were never used to put wine in, but simply to keep “water” in for the various purposes of ablution. A large number was used on this occasion, because there were many guests.