Albert Barnes on John 13:14-15

Ye also ought to wash, &c. Some have understood this literally as instituting a religious rite which we ought to observe; but this was evidently not the design; for,

1st. There is not evidence that Jesus intended it as a religious observance, like the Lord's Supper or the ordinance of baptism.

2nd. It was not observed by the apostles or the primitive Christians as a religious rite.

3rd. It was a rite of hospitality among the Jews, a common, well-know thing, and performed by servants.

4th. it is the manifest design of humility; to teach them by his example that they ought to condescend to the most humble offices for the benefit of others. They ought not to be proud, and vain, but to regard themselves as the servants of each other in every way. And especially as they were to be founders of the church, and to be greatly honoured, he took this occasion of warning them against the dangers of ambitions, and of teaching them, by an example that they could not forget, the duty of humility.