Ruth 3:3-4

3Wash thyself therefore, and anoint thyself, and put thy raiment upon thee, and go down to the floor; make not thyself known to the man, until he shall have done eating and drinking.

4And it shall be, when he lies down, that thou shalt mark the place where he shall have lain down, and thou shalt go in, and uncover his feet, and lay thyself down; and he will shew thee what thou shalt do.