Leviticus 19:13

19:13 You must not oppress your neighbor or commit robbery against him. You must not withhold the wages of the hired laborer overnight until morning.

Leviticus 25:50

25:50 He must calculate with the one who bought him the number of years from the year he sold himself to him until the jubilee year, and the cost of his sale must correspond to the number of years, according to the rate of wages a hired worker would have earned while with him.