2 Samuel 11:1

And it came to pass, after the year was expired, literally, "at the return of the year," when spring set in, when the close of the rainy season made operations in the field possible, at the time when kings go forth to battle, starting out for the season's campaigns, that David sent Joab and his servants with him and all Israel, the military chieftains with the entire regular army; and they destroyed the children of Ammon, overthrowing their smaller cities, devastating their land, and putting the inhabitants to death, and besieged Rabbah, the capital, which was strongly fortified. But David, instead of joining his army in the field, tarried still at Jerusalem, this life of comparative ease offering the occasion for the transgression: for, as the proverb has it: An idle brain is the devil's workshop.