serve two masters
To take orders from two superiors or two conflicting parties.
I suspect that Mr Paisley would have been familiar with the biblical quotation: "No man can serve two masters - you cannot serve God and Mammon" (Matthew 6 v 24).
ADJ.
against, all, greater, own, wise
She had to work against all the masters of the old academy to get her ideas accepted.
VERB + MASTERS
can't, choose, obey, observe, rebelled, remain, serve
The employees who rebelled against their masters eventually found better jobs elsewhere.
MASTERS + NOUN
cat, cats, contribution, degree, physics, servants, world
She earned her masters degree in physics from a top university.
PREP.
in, with
She studied hard and eventually earned her masters in chemistry.
ADV.
also
She also masters the art of public speaking after years of dedicated practice.