بَارَكَ اللَّهُ لَكَ وَبَارَكَ عَلَيْكَ وَجَمَعَ بَيْنَكُمَا فِي خَيْرٍ

BaarakAllaahu laka, wa baaraka 'alayka, wa jama'a baynakumaa fee khayr

May Allah bless you, and shower His blessings upon you, and join you together in goodness. Abu Hurairah (RA) said, "The Messenger of Allah (ﷺ) used to say this to congratulate the newlyweds."

Reference: Sahih (Albani). Abu Dawud: 2130