I needed to pray for power, and was at maybe... 85% health? The tooltip on screen said to pray for power regeneration (I was at about 30/500 power).
I prayed, and got healed instead.

I don't know whether the prayer effect was wrong or the tip was wrong, but they should definitely match. (Although, in this case I definitely wanted power - it's possible I could have gotten hit the next turn and gotten health AGAIN when I tried again)

This was on latest steam version (3.1.6?)