The 257th prohibition is that we are forbidden from giving a Jewish servant degrading and humiliating work, as a Canaanite servant would do.
The source of this prohibition is G‑d's statement1 (exalted be He), "Do not work him like a [Canaanite] servant."
In the words of the Sifra: "You shall not have him carry in a linta2 behind you, nor carry your things before you to the bathhouse." A linta is a small mat that one rests on after becoming tired from exercise. A servant customarily picks it up and carries it after his master. We are prohibited from giving any such jobs to a Jewish servant. He may be given only such jobs that an employed worker would agree to do. This is seen from G‑d's statement3 "He shall be with you just like an employee or a resident hand."