The full meaning of this statement can be made explicit. Alternate translation: "so that he will have his coat to keep himself warm when he sleeps, and he will be grateful to you" (See: [[rc://en/ta/man/translate/figs-explicit]])
This is a coat or other clothing that keeps a person warm at night. This was probably the "pledge" Moses was speaking of in [Deuteronomy 24:10-12](./10.md).