The Third Sunday of Advent takes its name from the entrance chant at Mass:
Rejoice in the Lord always; again I say, rejoice. Let your forbearance be known to all, for the Lord is near at hand; have no anxiety about anything, but in all things, by prayer and supplication, with thanksgiving, let your requests be known to God. Lord, you have blessed your land; you have turned away the captivity of Jacob.
— Philippians 4:4–6; Psalm 85 (84):1