Reference for Pesachim 191:20

אלא מעתה (שמות יב, מה) תושב ושכיר לא יאכל בו הכי נמי דבו הוא אינו אוכל אבל אוכל הוא בפסח דורות אמר קרא ועבדת אלא בו למה לי בו המרת דת פוסלת ואין המרת דת פוסלת בתרומה

Then what is the purpose of 'thereof'? - In that case only ['thereof'] does apostasy disqualify, but apostasy does not disqualify in the case of terumah - Now it is necessary that an uncircumcised person should be stated, and it is necessary that an alien should be stated. For if the Divine Law stated an uncircumcised person, [I would say that he is disqualified] because he is repulsive, but an alien is not repulsive [so] I would say [that he is] not [excluded from the Passover-offering]; hence [an alien] is necessary.

Jastrow