"in his ear": I might think, at the side of his ear; it is, therefore, written (Devarim 15:17) "in his ear and the door," whereby we are apprised that he pierces his ear (with the top of the awl) until it reaches the door.
"and he shall be unto you a servant forever" — the "forever" of Yovel. — But, perhaps, "forever" literally! — It is, therefore, written (Vayikra 25:10) "And each one of you will return to his holding" (at the Yovel). Why, then, is it written "a servant forever"? For I might think that (after his ear is bored) he serves only six years, so that his end (i.e., the end of his servitude) not be graver than his beginning; it is, therefore, written "a servant 'forever'" — even thirty years, even forty, until the Yovel. "and he shall be unto you a servant forever," and, elsewhere, (Vayikra 21:5) "and he shall serve him forever" — not his son and not his daughter — whence it is ruled: A Hebrew man-servant serves the son, but not the daughter. One whose ear was bored and one who was sold to a gentile serves neither the son nor the daughter. Whence is it derived that what is stated here (Devarim) applies there (Vayikra), and what is stated there applies here? From "forever" (Devarim 15:17) - "forever" (Vayikra 21:5), for an identity (gezeirah shavah).