After marriage, what if neither of the spouses are ready to have children, but have sexual desires? When the spouses consummate their marriage and have sexual intercourse, is it permissible to use birth control?
The Sahabah (Companions of the Prophet) practiced a form of birth control called Azl (coitus interruptus). There are several hadith about the matter, some listed here. In the hadith, the Prophet didn't forbid the practice but remarked that when Allah wills a creation it comes into being. Indeed there is a hadith in which the Prophet himself verbally permitted a person to practice it:
Jabir reported that a man came to Allah's Messenger (ﷺ) and said: I have a slave-girl who is our servant and she carries water for us and I have intercourse with her, but I do not want her to conceive. He (the Prophet) said: Practise 'azl, if you so like, but what is decreed for her will come to her. The person stayed back (for some time) and then came and said: The girl has become pregnant, whereupon he said: I told you what was decreed for her would come to her. Sahih Muslim 16/159
In another narration:
"We said: 'O Messenger of Allah! We practice Azl, but the Jews claim that it is minor infanticide.' So he said: 'The Jews lie. When Allah wants to create it, nothing can prevent Him.'" Tirmizi 11/58
The opinion of the majority of the scholars among both the Sunnis and Shia is that birth control is permissible (though sometimes disliked), provided that the wife consents.
This text lists several related references to classic books of Islamic jurisprudence of all four schools of thought among the Sunnis:
The Hanafis regard Azl as permissible, though some mandate that the wife's consent be sought, while others allow it regardless of the wife's consent in specific circumstances.
The Malikis regard Azl as permissible, subject to the consent of the wife. Some allow compensation to be paid to the wife to obtain her consent.
The Shafis regard Azl as permissible though makruh (disliked). They disregard the wife's consent since they consider that ejaculation is under the husband's domain. A minority regard Azl as forbidden.
The Hanbalis regard Azl as permissible. The wife's consent is to be sought except in extraordinary circumstances. Some say that Azl is mandatory when in enemy territory.
It is generally thought that it is impermissible in Islam. The rationale being that this is kind of impediment in the natural process of procreation. There is a Hadith whereby Prophet Mohammad (PBUH) prayed for a Maximum count of people born so that his Ummah would exceed the disbelievers. This provides the strength to the above notion. Yet another point is that Allah has taken the responsibility of providing sustenance to each and every being born.There are, however, instances in the Islamic parlance where Shabah have been mentioned to have practiced "AZAL" (withdrawal) to prevent unwanted conceptions. Prudence, on the other hand, would demand restraint in procreational activities; which may, in the end, prove to be superfluous. Allah knows best. Thanks