Yevamot 48A

ומותר בה מיד.

And he is permitted to marry her immediately afterward, without the need for her to undergo the process described in the Torah. The fact that the Rabbis do not suggest this course of action is evidently because they hold that even if she were to be rendered a slave and then immersed for the sake of emancipation, she would become Jewish only if she also accepted upon herself the yoke of mitzvot. Rav Sheshet assumes that the Rabbis would similarly rule that a regular slave who was immersed for the sake of emancipation becomes Jewish only if he also accepts upon himself the yoke of mitzvot.

אמר רבא: מאי טעמא דרבי שמעון בן אלעזר ⁠— דכתיב: ״כל עבד איש מקנת כסף״. ״עבד איש״, ולא עבד אשה? אלא ״עבד איש״⁠ — אתה מל בעל כרחו, ואי אתה מל בן איש בעל כרחו.

Rava said: What is the rationale for R' Shimon ben Elazar’s opinion? As it is written with regard to the Paschal lamb: “Every slave of a man that is bought for money, when you have circumcised him, then he may eat of it” (Exodus 12:44). Could the use of the phrase “slave of a man,” rather than just: Slave, possibly indicate that the verse applies only to a man’s slave but not a woman’s slave? Certainly not; rather, the phrase “slave of a man” means that the slave himself is a man, i.e., an adult, and teaches that a slave who is a man you may circumcise against his will, and there is no need for him to accept upon himself the yoke of mitzvot, but you may not circumcise a non-Jew’s son who is a man, i.e., an adult who is not a slave, against his will.