David, in his mercy, obtained the throne of a kingdom for all generations.
David inherited the throne of the kingdom forever because he was merciful.
David by his mercy obtained the throne of an everlasting kingdom.
David was made king and was given the promise that his descendants would always be kings because of his steadfast loyalty to God.
David inherited the throne of a kingdom forever and ever for being merciful.
David's family will rule as kings forever because David had mercy on others.