Orlas basar
The Torah in our parsha uses the expression “yimol *”bsar** orlaso” but when speaking elsewhere of the mitzvah to mal avadim so they can eat korban pesach the Torah uses the expression “u’malta oso,” without the word “basar.’ Why the difference?
Chasam Sofer explains that a Jew, whether he has a physical milah or not, is not an orlas lev. He has an inherent connection to Hashem. The Mishna in nedarim writes that someone who takes a neder that applies to aralim does not mean to include Jews, even those who might not have a milah. The milah just removes orlas *”basar,** the physical orlah.
The same is not true for an eved who lacks that inherent connection. He must undergo a complete transformation through the milah.
From Divrei Chaim, here.