My prefix is a big ol' ass,
My infix always comes before;
My suffix straight up lies bruv',
About the answer that I bore,
I told ya who I am already, know what I mean?
The Accepted answer should both answer the Riley and find all the hidden clues.
Clues are hidden in both the title and the rhyme, once you find the answer everything will make sense, Good Luck.
Found after rainfall, in all continent,
Can be found also in sinful intent.