פירוש על קידושין 34:5

The baraita reads Deuteronomy 15:12 as teaching that the slave works for the one who bought him, but not his heir. In this context, the heir referred to must be someone besides the son, such as a brother or daughter. Exodus 21:2, where the word “you” is not found, is read as teaching that he does work for the son should the master die.