Albert Barnes on John 2:9

And knew not whence it was. This is said, probably, to indicate that his judgment was not biased by any favour, or any want of favour, toward Jesus. Had he known what was done, he would have been less likely to have judged impartially. As it is, we have his testimony that this was real wine, and of so fine a body and flavour as to surpass that which had been provided for the occasion. Everything in this miracle shows that there was no collusion or understanding between Jesus and any of the persons at the feast.

(g) "servants" Ps 119:100, Jn 7:17