Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear brother in Islam, we highly appreciate the great confidence you place in us. May Allah reward you abundantly for your interest in knowing the teachings of Islam.
The preservation of the human race is unquestionably one of the primary objectives of marriage, along with giving the man and woman a halal outlet for their natural sexual urges. Accordingly, Islam encourages having many children and blesses both male and female offspring.
Answering your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states,
Islam encourages us to marry and procreate. The Prophet (peace and blessings be upon him) said, “Marry and procreate.” Procreation is definitely one of the stated purposes of marriage in Islam. Children are Allah’s gifts, which we must welcome and cherish as a divine gift.
Islam is opposed to ways of life which consider children as a burden; the unfortunate outcome of such hedonistic philosophies is to prefer pets such as dogs and cats over children. Muslims must never be carried away by such materialistic philosophies; they can immunize themselves against such negative influences by strictly conforming to the Qur’anic teachings on marriage and procreation.
Viewed from this perspective, Islam does not look favorably at family planning if it is carried out for the simple reason of enjoyment and unwillingness to take on the responsibility of parenting.
Having said this, however, I must say the following. Since Islam considers quality more important than quantity, if the couple is resorting to contraception for any one of the following reasons, it may be considered permissible:
1- If both spouses are students whose academic performance would be adversely affected by taking on the added responsibility of parenting.
2- If they are too young to shoulder parental responsibilities.
3- If one or both of them are weak or sick and expect to take on the responsibility when the condition improves.
4- If they are burdened with responsibilities of taking care of their parents in advanced age, which drain them physically and emotionally.
5- If they are doing so only for a limited time (for instance the first one or two years) in order to be able to get to know each other, and thus prepare themselves better for shouldering such responsibilities.
6- If they are doing so in order to have gaps between pregnancies with a view to provide quality care and attention to the existing children.
If the wife cannot bear children because of medical reasons.
Now coming to the final point in your question, I must say:
Since the right to have children is shared equally between husband and wife, neither one of them should resort to contraception unilaterally. Rather, he or she is allowed to do so only through consensual agreement. The only exception to this rule is when the pregnancy is determined to be a risk to the wife’s life. In this case, she does not need permission of her husband to resort to contraception.
Allah Almighty knows best.