I’ve always assumed that David had sex with Bathsheba once. However, the text says that when David first saw her, she was bathing to purify herself of her uncleanness (2 Sam 11:1-5). This is referring to the bathing a woman would undergo after her menstrual cycle ended. Since one is least fertile immediately following menstruation, this suggests that David’s fling with Bathsheba was no one-night stand. Bathsheba probably remained with David for a number of days before returning to her house, during which they had sexual relations multiple times. If so, David’s sin was not a one-time mistake, but an ongoing sin.