1 Chronicles (Author Compiled by Isaiah and Ezra from records of Nathan, Gad, Iddo, Ahijah, Jehu and others.)
21:8And David said to God, I have sinned greatly, in that I have done this thing; and now, I beseech thee, put 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.