First, exhortation to showing affection and mercy even if love is not existent
Allah (may He be Exalted) says: "And among His Signs is that He created for you wives from among yourselves, that you may find repose in them, and He has put between you affection and mercy. Verily, in that are indeed signs for a people who reflect." (1) i.e., made between you intimacy through marriage relationship
(and mercy) which He showed to you, thereby you showed mercy to one another without having prior knowledge nor a kin relationship. However, this intimacy and that mercy are from Allah (may He be Exalted) because a man keeps his wife either because he loves her, out of mercy to her because of his children, she needs him in expenditure, or because they have something in common. (2)
Love is not the secret for the continuation of marital life and its happiness, but kind treatment, intimacy, and showing mercy to one another. In spite of the prohibition of laying and intensifying its punishment, the Shari`ah permitted part of it to the spouses so that each one of them would draw nearer to the other. Um Kulthum, the daughter of `Uqbah (may Allah be pleased with her), narrated that she heard the Messenger of Allah (peace be upon him) saying: "He who makes peace between the people by inventing good information or saying good things, is not a liar." She said: I did not hear the Prophet (peace be upon him) permits something of what the people consider as laying but in three positions: In war, in reconciliation between the people, and the speech of a husband with his wife and the speech of a wife with her husband. (3)
Likewise, doing all things that may achieve harmony and mercy between the spouses of the things which Allah permitted.
(1) Surat Ar-Rum: 20.
(2) See: Tafsir Al Qur'an Al `Azhim 6/309, Ad-Dur Al Manthur 7/56, Fathul-Qadir 4/312, and Tafsir At-Tabary 20/86.
(3) Reported by Muslim in the chapter on the prohibition of lying and explaining the permissible type, Hadith No. 6800 - 8/28 and see the commentary of An-Nawawy on Sahih Muslim 16/158.