May God arise, may his enemies be scattered;
    may his foes flee before him.
² May you blow them away like smoke—
    as wax melts before the fire,
    may the wicked perish before God.
³ But may the righteous be glad
    and rejoice before God;
    may they be happy and joyful. Psalm 68:1-3

What about being before God makes you rejoice?