What are the implications of "Ki Avadai Heim"?
Rashi: It is a reminder that Hashem's document (that we are His Avadim) 1 precedes the document of sale that the Eved Ivri gave to his master (and He acquired us on condition that we are not sold 'Mimkeres Eved' - Sifra)..
Seforno: Even though the Eved acquired a master for himself, and therefore deserves to perform whatever tasks are placed upon him, due to the fact that he is Hashem's Eved, he does not have the authority to sell himself as an Eved, unconditionally.
See Torah Temimah, note 221.
Having already written (in Pasuk 39)"Lo Sa'avod bo Avodas Aved", why does the Torah repeat "Lo Yimachru Mimkeres Aved"?
Rashi (citing the Sifra): It is a prohibition against selling an Eved Ivri in the way that one sells an Eved Cana'ani - by announcing his sale or by placing him on the 'stone of sale' (or by selling him in an alleyway - Sifra). 1
Sanhedrin, 86a: It is the warning against selling someone after having kidnapped him. 2
