Sotah 3B

ורבי עקיבא ⁠— אם כן, ליכתוב רחמנא ״לה״ ולישתוק, ״יטמא״ למה לי? שמע מינה.

And what does R' Akiva respond to this claim? The Talmud answers: If so, that the verse serves to render it prohibited for a priest to become impure to bury a limb, then let God write: “And for his sister a virgin, that is near to him, that has had no husband, for her,” and then be silent. Why do I need the verse to write: “May he become impure”? Learn from the additional phrase that making himself impure is mandatory.

ורבי ישמעאל, איידי דכתב ״לה״, כתב נמי ״יטמא״. לכדתני דבי רבי ישמעאל. דתנא דבי רבי ישמעאל: כל פרשה שנאמרה ונישנית, לא נישנית אלא בשביל דבר שנתחדש בה.

And how does R' Yishmael explain the additional phrase? Since the verse wrote: “For her,” it also wrote: “May he become impure,” for the same reason as was taught by the school of R' Yishmael. As the school of R' Yishmael taught: Every passage in the Torah that was stated and repeated, was repeated only for the novel element introduced therein. Therefore, it is possible that the verse serves to teach the halakha that a priest may not become impure in order to bury a limb, and that would account for the repetition of the phrase “may he become impure” as well.

״לעלם בהם תעבדו״⁠ — רשות, דברי רבי ישמעאל. רבי עקיבא אומר: חובה.

The Talmud discusses the third dispute between R' Yishmael and R' Akiva. The verse states: “Of them may you take your bondmen forever” (Leviticus 25:46), i.e., the halakha that one keeps his Canaanite slave forever, is optional; this is the statement of R' Yishmael. One is not enjoined against emancipating a Canaanite slave, but one is permitted to keep a Canaanite slave forever. R' Akiva says: It is mandatory, and one is prohibited from freeing his Canaanite slave.