Yoreh Deah Siman 267 Seif 4

 

ד לָקַח עֶבֶד גָּדוֹל מֵהָעוֹבֵד כּוֹכָבִים, וְלֹא רָצָה הָעֶבֶד לִמֹּל, מְגַלְגֵּל עִמּוֹ כָּל י”ב חֹדֶשׁ. יֶתֶר עַל כֵּן, אָסוּר לְקַיְּמוֹ כְּשֶׁהוּא עָרֵל, אֶלָּא חוֹזֵר וּמוֹכְרוֹ לְעוֹבֵד כּוֹכָבִים.

Seif 4

 

When one purchases a slave from an idolater and the slave does not want to be circumcised, we are patient with him for a total of twelve months. Any more than this it is forbidden to hold on to an uncircumcised individual so one must then sell him to idolaters..