Prophet(SAW)'s Dua for newlyweds
When supplicating for the newlywed, the Prophet Mohammad (SAW) would say:
بَارَكَ اللهَ لَكَ وَبَارَكَ عَلَيْكَ وَجَمَعَ بَيْنَكُمَا فِي خَيْرٍ
(Barak Allahu laka wa baraka alaik, wa jama a bainakuma fi khair)
May Allah bless you and send blessings upon you, and bring goodness between you.