Yevamot 70B

אלמא לא קני ליה רביה. הכא נמי לא קני ליה רביה, אלא לאפנויי.

Apparently his master does not acquire his body and thereby effect a change in his personal status; rather, he remains a Jew in every sense. Here too, then, with regard to the Paschal lamb, his master does not acquire his body as a slave, and so he is obviously obligated in the mitzva of the Paschal lamb. Rather, the phrase is superfluous and was written only to be available to teach a different matter.

ואכתי מופנה מצד אחד הוא, ושמעינן ליה לרבי אלעזר דאמר: מופנה מצד אחד, למדין ומשיבין?

The Talmud poses a question: And yet there is still a difficulty: The verbal analogy is available from only one side, as only the phrase with regard to the Paschal lamb is superfluous in its context, and we heard R' Elazar, who said with regard to a verbal analogy available from only one side that one can derive from it, and one can also refute it logically if there is reason to distinguish between the two cases. Since there are grounds here for differentiating between the two halakhot in this case, why is the verbal analogy upheld?

כיון דלגופיה לא צריך ⁠— שדי חד אלמד ושדי חד אמלמד, והוה ליה גזירה שוה מופנה משני צדדין.

The Talmud answers: Since the phrase “a sojourner and a hired servant” is not needed for its own matter, there are two superfluous terms, and one may cast one superfluous term on the halakha with regard to which it is learned that teruma may not be eaten by one who is uncircumcised, and one may cast the other one on the halakha with regard to the Paschal lamb that teaches this, and in this manner it is like a verbal analogy that is available from both sides, which cannot be refuted.