وَعَنْ أَبِي هُرَيْرَةَ
أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ كَانَ إِذَا رَفَّأَ الْإِنْسَانَ إِذَا تَزَوَّجَ قَالَ: «بَارَكَ اللَّهُ لَكَ وَبَارَكَ عَلَيْكُمَا وَجَمَعَ بَيْنَكُمَا فِي خَيْرٍ»
When the Prophet (sallallahu alayhi wa sallam) congratulated* a man on his marriage he said, “God bless you, bless you both, and prosper your union.” *The verb used is raffaa which originally meant saying to someone who had just been married, “may the marriage produce close union and sons.”
It is said that because this was a phrase used in pre-lslamic times, the Prophet (sallallahu alayhi wa sallam) substituted for it the words used in this tradition. The verb thus develops simply the meaning of congratulating without in itself involving any particular formula.