Reference for Yevamot 8:2
אֵיזֶהוּ פְצוּעַ דַּכָּא, כֹּל שֶׁנִּפְצְעוּ הַבֵּיצִים שֶׁלּוֹ, וַאֲפִלּוּ אַחַת מֵהֶן. וּכְרוּת שָׁפְכָה, כֹּל שֶׁנִּכְרַת הַגִּיד. וְאִם נִשְׁתַּיֵּר מֵהָעֲטָרָה אֲפִלּוּ כְּחוּט הַשַּׂעֲרָה, כָּשֵׁר. פְּצוּעַ דַּכָּא וּכְרוּת שָׁפְכָה, מֻתָּרִין בְּגִיּוֹרֶת וּמְשֻׁחְרֶרֶת, וְאֵינָן אֲסוּרִין אֶלָּא מִלָּבֹא בַקָּהָל, שֶׁנֶּאֱמַר (דברים כג), לֹא יָבֹא פְצוּעַ דַּכָּא וּכְרוּת שָׁפְכָה בִּקְהַל ה':
A petzuah dakka is one whose testicles have been injured, even one of them. And a k'ruth shafchah is one whose membrum is cut. And if there remained even a hairs-breadth of the corona [If it were cut from the corona down], he is fit, [the "membrum" being from the corona upwards towards the body. The corona (atarah) is the row of flesh surrounding the circumcision site. Whether the membrum is injured as by sword or knife, or whether it was crushed and became small of itself — whether it was cut in the membrum or the testicles or the testicular cords — all of these render him unfit. And this is so only when man is the cause; but if illness is the cause, all is kasher.] A petzua dakka and a k'ruth shafchah are permitted to a proselyte and to a freed bondswoman. And they are forbidden only to enter the congregation, it being written (Deuteronomy 23:2): "A petzua dakka and a k'ruth shafchah shall not come into the congregation of the L rd."