2 Samuel 5:13

And David took him more concubines and wives of Jerusalem, according to the custom of Oriental monarchs, after he was come from Hebron. In the law pertaining to kings, Deuteronomy 17:17, the taking of many wives had indeed been forbidden the kings of Israel, and David found out to his sorrow that his following the custom of the heathen kings brought him much trouble and heartache. And there were yet sons and daughters born to David.