Samuel II Chapter 11 tells of David committing adultery with Bathsheba. Whether or not she was actually considered to be married is a matter of debate, as sourced here. According to those who say ...
Tosafos version of Rashi in the Gemara 9b implies that there was a get on condition that Uria (Bat shevas husband) wont come back. So if David didn't know if Uria would come back or not how could he ...