19 Soa when the time came for Merab, Saul’s daughter, to be given to David, she was given in marriage to Adriel of Meholah.

Read 1 Samuel 18:19 Using Other Translations

But it came to pass at the time when Merab Saul's daughter should have been given to David, that she was given unto Adriel the Meholathite to wife.
But at the time when Merab, Saul's daughter, should have been given to David, she was given to Adriel the Meholathite for a wife.
So when the time came for Saul to give his daughter Merab in marriage to David, he gave her instead to Adriel, a man from Meholah.