1 Chronicles (Author Compiled by Isaiah and Ezra from records of Nathan, Gad, Iddo, Ahijah, Jehu and others.)
21:8And David said unto God, I have sinned greatly, because I have done this thing: but now, I beseech thee, do away the iniquity of thy servant; for I have done very foolishly.
Original from The Bible Foundation - bf.org. They claim public domain status for their original text.