Verb
serve two masters (third-person singular simple present serves two masters, present participle serving two masters, simple past and past participle served two masters)
(idiomatic) To take orders from two superiors or two conflicting parties.
Nerds serve two masters. They want to be popular, certainly, but they want even more to be smart. And popularity is not something you can do in your spare time, not in the fiercely competitive environment of an American secondary school. Paul Graham
A life is either all spiritual or not spiritual at all. No man can serve two masters. Your life is shaped by the end you live for. You are made in the image of what you desire. Thomas Merton
No man can serve two masters. English Proverb
One cannot serve two masters. Hungarian Proverb
Nobody can serve two masters. Catalan Proverb