Yevamos8: 2
אֵיזֶהוּ פְּצוּעַ 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 מִלָּבוֹא בַקָּהָל, שֶׁנֶּאֱמַר (דברים כג, ב): ,,לֹא יָבֹא פְצוּעַ דַּכָּא וּכְרוּת שָׁפְכָה בִּקְהַל ה' ”.
Who is [considered] someone with mutilated testicles? Anyone whose testicles were cut, even if only one of them. And [who is considered] a person whose phallus was severed? Anyone whose phallus was cut off; [however,] if even a hairsbreadth of the corona remained, he is fit.  Persons with mutilated testicles or a severed phallus are permitted to [marry] a convert or an emancipated slavewoman; they are forbidden only to enter into the congregation, as it is stated (Deut. 23:2): A person with mutilated testicles or a severed phallus may not enter the congregation of God.