Mahr in Islam is an object of value or money a husband offers his wife at the time of nikaah as a token of appreciation of her willingness to marry him—it is a good will gesture, and informs the wife and her family that as Muslims, when a man takes on the responsibility of being a husband, then he willfully and willingly will sustain his wife with financial support. Mahr underscores the wife’s legal right of ownership in Islam; anything a husband gives his wife is hers to keep forever. From the outset, Islam wanted to show that the responsibility in providing for the wife lies on the husband.

Allah says, “(Oh men!) give women their mahr as an obligation…” (s. Al-Nisaa v. 4) .

The mahr a husband gives to his wife cannot be less than ten dirhams, which is approximately 31 grams of silver. There is no legal cap on what a woman can demand, but it should not be such an amount that the husband will fall into straits trying to pay it. The Prophet (peace be upon him said), “The best of mahrs is the easiest (most affordable)” and, "The marriage with the most blessing is the one with the least burden.”

The amount Ali gave to Fatima radhiyallahu anhuma, the daughter of the Prophet sallallaahu alayhi wasallam, was equivalent to 1469.60 grams of silver. This amount, known as the Mahr al-Fatimi, is commonly seen as the sunnah amount.