Yoreh Deah Siman 267 Seif 5

 

ה אִם מָל אֶת עַבְדּוֹ וְהִטְבִּילוֹ בְּעַל כָּרְחוֹ לְשֵׁם עַבְדוּת, לֹא עָשָׂה כְּלוּם.

Seif 5

 

If one circumcised and immersed his slave against his will for the sake of becoming a slave,  his actions are of no consequence.