Charles Ellicott Commentary Numbers 11:18

"And say thou unto the people, Sanctify yourselves against to-morrow, and ye shall eat flesh; for ye have wept in the ears of Jehovah, saying, Who shall give us flesh to eat? for it was well with us in Egypt: therefore Jehovah will give you flesh, and ye shall eat." — Numbers 11:18 (ASV)

Sanctify yourselves against to-morrow. —(). The Israelites were required to sanctify themselves by purification for the more immediate manifestation of the Divine presence, although their request was a sinful one, and was granted in judgment as well as—or even more than—in mercy. Compare to Psalms 106:15: And he gave them their request; but sent leanness into their soul.