Job 21:15
What is the Almighty, that we should serve him? and what profit should we have, if we pray to him?
Nave's Topical Index—AKJV

Malachi 3:14
You have said, It is vain to serve God: and what profit is it that we have kept his ordinance, and that we have walked mournfully before the LORD of hosts?
Nave's Topical Index—AKJV