Matthew Poole and continuators on Numbers 11:18

18 And say thou unto the people, Sanctifie your selves against to morrow, and ye shall eat flesh: (for ye have wept in the ears of the LORD , saying, Who shall give us flesh to eat? for it was well with us in Egypt) therefore the LORD will give you flesh, and ye shall eat.

(i. e.) Prepare your selves, either to receive the miraculous blessings of God, the flesh you desire: or rather, prepare to meet thy God, O Israel, in the way of his judgments, and to receive the punishment which God will inflict upon you, for it is evident from ver. 20. that God answered them with a curse in stead of a blessing. Prepare your selves by true repentance, that you may either obtain some mitigation of the plague, or, whilest your bodies are destroyed by the flesh you desire and eat, ver. 33, 34. your souls may be saved from the wrath of God. Sanctifying is oft used for preparing, as Ier. 6. 4. and 12. 3. and 51. 28.

Not secretly in your closets, but openly and impudently in the doors of your tents, ver. 10. calling heaven and earth to witness your cries and complaints.