Reference for Chullin 77:8

רבי יוחנן אמר פסולה מחשבין מעבודה לעבודה וילפינן חוץ מפנים

Resh Lakish says: it is permitted', because he does not accept the principle, 'a wrongful intention expressed during one service with regard to another service is of consequence [in the case of idolatry]', for one must not draw any analogy between acts performed inside and acts performed outside.

Jastrow