Abu Hurayrah (may Allah be pleased with him) narrated that when the Prophet (peace be upon him)congratulated a man on his marriage, he said: "May Allah bless for you, and may He bless on you both, and combine both of you in good (works)."(1) Ar-Rifa' means assembly, harmony, blessing, and increase.(2)
The custom of the Arabs regarding the person who marries is to say to him: "Bir-Rafa' wal Banin." However, the Shari`ah forbade that and replaced it with the above mentioned supplication. So, it is reprehensible to say to a person: "Bir-Rafa' wal Banin."
Scholars have differed regarding the cause of prohibition: It was said: Because the saying does not contain thanking, praising, or mentioning the name of Allah. It was also said: Because it contains a reference to the hatred of girls and the love of boys because it mentions them only.
There is no doubt the invocation is comprehensive, so the supplication includes: "May Allah bless for you," which means: May Allah increase goodness for you, and the meaning of blessing is increase and happiness. "And may He bless on you both," in another narration: "and may Allah bless you all" by sending down goodness, mercy, sustenance, and bless the offspring. "and combine both of you in good (works)." i.e., in obedience, health, safety, good treatment, and multiplying good offspring.
It was said: The Messenger (peace be upon him) first said "May Allah bless you" because he is the one for whom people invoke. Then he said: "May Allah bless you both" which means may Allah grant you offspring because it is the main objective of marriage. Then he delayed Kind treatment and enjoyment because he wanted to stress the importance of offspring then everything else is subservient. (3)
(1) Reported by Abu Dawud in the book of marriage, chapter on what is to be said for the newly married person, Hadith No. 2130 - 2/248 and At-Tirmidhy in the book of marriage, chapter on what is to be said for the newly married couples, Hadith No. 1097 - 2/276 and said: This is a good and authentic Hadith. An-Nasa'y also reported the Hadith in As-Sunan Al Kubra in the book of `Amal Al Yawm Wa Al Laylah, chapter on what should be said for the newly married couples, Hadith No.10089 - 6/73, Ibn Majah in the book of marriage, chapter on preparation of marriage, Hadith No. 1905 - 1/614, Ad-Darimy in the book of marriage, chapter on what is to be said for the man when he gets married, Hadith No. 2/134, Ahmad 2/381, and reported by Al Hakim in the book of marriage, chapter on invoking Allah for the newly married couples at marriage 2/183 and said: this Hadith was reported according to the conditions of Muslim; and Adh-Dhahaby agreed to his judgment on the Hadith.
(2) An-Nihayah Fi Gharib Al Athar 2/591.
(3) See: Fathul-Bary 9/222, At-Taysir Bisharh Al Jami` As-Saghir of Al Munawy 1/169, Fayd Al Qadir 5/176, Mishlatul-Masabih 8/427, Wa Mar`at Al Mafatih of Al Mubarakfury 8/198.