Vessels no man can serve, the Good Book says? (3-7)

I believe the answer is:

two-masters

I believe this is a double definition.

'vessels' is the first definition.
(I've seen this before)

'no man can serve the good book says?' is the second definition.
('No man can serve two masters' - Matthew 6:24)

I've seen this clue in The Times.

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