Es antes la obligación que la devoción

[ROBINDESBOIS]

In English?

[Perikles]

Business comes before pleasure. :)

[wrholt]

And also "business before pleasure". Either way is equivalent, and saying/writing it without "come" may be more typical of proverbs.

[Glen]

Even more succinctly, "Duty first."

[JPablo]

I agree.
Robin, you can also check the Idioms in Tomisimo, as you can see here,
http://www.tomisimo.org/idioms/es/primero-la-obligacion-y-luego-la-devocion-9765.html

(By the way, more contributions in the Idiom section, will always be welcome, as these are very easy to access, and to use...) (Just a plug... I mean, I couldn't miss this opportunity to get in a plug for the excellent section of Idioms...)