Charles Ellicott Commentary Exodus 40:31-32

"And Moses and Aaron and his sons washed their hands and their feet thereat; when they went into the tent of meeting, and when they came near unto the altar, they washed; as Jehovah commanded Moses." — Exodus 40:31-32 (ASV)

These verses are parenthetical. They interrupt the narrative of what Moses did “on the first day of the first month,” informing us of the use to which the laver was applied subsequently. (Compare Exodus 30:19-21.)