"Behold, piety is wisdom" (Job.28,28).

"Human wisdom consists in piety.
This you have in the book of the saintly Job,
for there he writes that Wisdom herself said to man,
'Behold, piety is wisdom.'
If, then, you ask what kind of piety she was speaking of,
you will find it more distinctly designated by the Greek term theosebeia, literally, 'the service of God.'
The Greek has still another word for "piety," ensebeia,
which also signifies 'proper service.' This too refers chiefly to the service of God.  
But no term is better than theosebeia,
which clearly expresses the idea of the man's service of God as the source of human wisdom.
When you ask me to be brief, you do not expect me to speak of great issues in a few sentences, do you?
Is not this rather what you desire:
a brief summary or a short treatise on the proper mode of worshipping [serving] God?
If I should answer
'God should be worshipped in faith, hope, love,'
you would doubtless reply that this was shorter than you wished,
and might then beg for a brief explication of what each of these three means:  
What should be believed, what should be hoped for, and what should be loved?
If I should answer these questions, you would then have everything you asked for in your letter."

                                                                                                         (Saint Augustine)