Praise be to Allah.
There is nothing wrong with one who is junub coming to receive well-wishers and to greet them and sit with them, because of the report narrated by al-Bukhaari (238) and Muslim (372) from Abu Hurayrah, that he met the Prophet (peace and blessings of Allaah be upon him) in one of the streets of Madeenah when he was junub. He slipped away and went to do ghusl, and the Prophet (S) noticed he was gone. When he came to him, he said: “Where were you, O Abu Hurayrah?” He said: O Messenger of Allaah, you met me when I was junub, and I did not like to sit with you until I had done ghusl. The Messenger of Allaah (S) said: “Subhaan-Allaah, the believer does not become naajis.”
But it is better for him to do wudoo’, because of the report narrated by Muslim (305) from ‘Aaishah who said: When the Messenger of Allaah (S) was junub and wanted to eat or sleep, he would do wudoo’ as for prayer.
And because the angels do not come close to one who is junub, as it says in the hadeeth from the Prophet (peace and blessings of Allaah be upon him): “There are three whom the angels do not approach: the dead body of a kaafir, the one who is perfumed with khalooq and the one who is junub, until he does wudoo’.” Narrated by Abu Dawood (4180); classed as hasan by al-Albaani in Saheeh Abi Dawood (3522).
“The one who is perfumed with khalooq” refers to a man who is wearing perfume containing saffron, because that involves frivolity and imitation of women. Fayd al-Qadeer (3/325).
See also question no. 6533.
As for these bad customs, people should be made aware and warned against them, because such gatherings are embarrassing for the newly-weds, and may cause them psychological distress that they do not need in these circumstances, i.e., when the man and his wife feel that his relatives and friends are waiting for them to finish what they are doing, so that they can congratulate them after that!
The time for offering congratulations is not limited to this embarrassing time. These congratulations can be offered during the wedding, or after that night, or at any other time. There is no point in singling out that time for congratulating the couple, apart from ancient foolish customs that have no basis in sharee’ah and serve no purpose according to common sense, and are not good manners.
And Allaah knows best.