Prophet (SAW)'s Prayers Congratulating the bridegroom

Recite:

بَارَكَ اللَّهُ لَكَ وَبَارَكَ عَلَيْكُمَا وَجَمَعَ بَيْنَكُمَا فِي خَيْرٍ

"May Allah grant you Barakaat (blessings) and descend His blessings on both of you and keep you united". (Ahmed, Tirmidhi)