Commentary for Avodah Zarah 40:18

ת"ש דתניא בהמה ע"מ לשחוט ושוחט דברי רבי יהודה רבי מאיר אומר אין מוכרין לו אלא שחוטה:

Come and hear: It has been taught: Cattle with the stipulation that he should slaughter it, and he then slaughters it, the words of R. Judah. R. Meir says: We may only sell it to them when slaughtered.

Daf Shevui to Avodah Zarah