Abu Hurayrah, Allah be pleased with him narrates that when the prophet of Allah, Allah send peace and blessings upon him would congratulate someone upon their marriage he would say:

May Allah bless you and shower His blessings on you and Allah unite you both in goodness.

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ حَدَّثَنَا عَبْدُ الْعَزِيزِ – يَعْنِى ابْنَ مُحَمَّدٍ – عَنْ سُهَيْلٍ عَنْ أَبِيهِ عَنْ أَبِى هُرَيْرَةَ أَنَّ النَّبِىَّ -صلى الله عليه وسلم- كَانَ إِذَا رَفَّأَ الإِنْسَانَ إِذَا تَزَوَّجَ قَالَ:

بَارَكَ الله لَكَ وَبَارَكَ عَلَيْكَ وَجَمَعَ بَيْنَكُمَا فِى خَيْرٍ

(رواه أبو داود، باب مَا يُقَالُ لِلْمُتَزَوِّجِ، ح/ ٢١٣٢)