Seeing as, on the one hand, we are obligated to kill all members of the seven Cana'ani nations, whilst on the other, we are not permitted to subjugate a fellow-Jew, who will perform the tasks that one may not command an Eved Ivri to do?
Rashi: Hence the following Pasuk permits making use of the surrounding nations, who are not Cana'anim, and whom one is therefore permitted to purchase as slaves. 1
See Torah Temimah, note 223.
Why does the Torah insert the (otherwise superfluous) words "asher Yih'yu lach"?
Sifra: To teach us that if a Yisrael has relations with his Shifchah Cana'anis and she bears him a son, he (the father) is allowed to take him as a slave.
What are the implications of "asher Sevivoseichem"?
Sifra: It implies that one is not permitted to purchase Avadim from Eretz Cana'an. 1
See Torah Temimah, note 225.
Why does the Torah insert the (otherwise superfluos) word "Meihem Tiknu Eved ve'Amah"?
Moshav Zekenim (citing Gitin 38a): To teach us that a Yisrael can purchase Nochrim (Kinyan ha'Guf - they become your property), but they cannot purchase a Yisrael (they can only acquire an Eved Ivri for his labor), or one another. 1
Sifra: To teach us that one may purchase not only their children as slaves, but also them.
Oznayim la'Torah: The Torah writes "Meihem Tiknu Eved ve'Amah" and not 'bahem Ta'avdu be'Farech' to teach us that, in contrast to other sales, it is preferable to purchase an Eved Cana'ani from Nochrim than from a Yisrael. 2
See Oznayim la'Torah, who gives two reasons for this ? one of them because it results in bringing another soul under the Wings of the Shechinah. Refer to 25:45:3:1.
Refer to 25:14:2.1:2.