Mishkat al-Masabih #2339

Abu Huraira said that when the Prophet congratulated* a man on his marriage he said, “God bless you, bless you both, and prosper your union.” *The verb used is raffa'a 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 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. Ahmad, Tirmidhi, Abu Dawud and Ibn Majah transmitted it.