Комментарий к Дварим 15:17

עבד עולם [AND HE SHALL BE THY] SERVANT עולם — One might think that עולם has here its usual meaning: for ever! Scripture, however, states, (Leviticus 25:10) “[And ye shall sanctify the fiftieth year and proclaim liberty throughout all the land unto all the inhabitants thereof] and ye shall return every man unto his family”. Consequently, you learn that it (what Scripture terms here עולם), can only mean the period until the termination of that Jubilee cycle (Mekhilta d'Rabbi Yishmael 21:6:6; cf. Rashi on that verse),

לך לעבד עולם, "for you as an eternal slave." Seeing that if the original master had died during the first six years of said servant's service he has to complete his term working for the master's son, the fact that he had his ear pierced לך, "for you," means that he will remain yours (the master's) forever but not your son's forever.

ואף לאמתך תעשה כן, to grant her a financial stake to establish herself.