What is the concept of social life after marriage in Islam? 1) Can a couple invite another friend couple on dinner at home? 2) Can they invite each other or visit each other home and share the joy, etc.?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

The family system in Islam is the best and most perfect system as it is legislated by Allaah, the Lord of the Worlds. It is He Who created all the creation so He knows what benefits them. Allaah Says (what means): {His is the creation and the command; blessed is Allaah, Lord of the worlds.}[Quran 7:54].

Among the most important things for legislating marriage in Islam is to achieve peace and tranquillity between the spouses. Allaah Says (what means): {It is He who created you from one soul and created from it its mate that he might dwell in security with her.}[Quran 7:189]. In order to achieve this security and tranquillity, the spouses should live honourably with each other. Allaah Says (what means): {And live with them in kindness.}[Quran 4:19] Allaah further Says (what means): {…And they (women) have rights (over their husbands as regards living expenses, etc.) similar (to those of their husbands) over them (as regards obedience and respect, etc.) to what is reasonable.}[Quran 2:228].

So it is permissible in principle to make use of any means which does not contradict the Islamic Law and through which social harmony could be achieved.

Therefore, there is no harm to exchange visits and invitations between various families provided religious requirements are met, like avoiding mixing between men and women and the like; this includes the permissibility of inviting a couple for dinner. 

Allaah Knows best.