Mahr:
Mahr is the gift that is given by the husband to his wife at wedding. It can be anything in any amount, as agreed by the bride and bride-groom.Mahr is a token commitment of the husband's responsibility and may be paid in cash, property or movable objects to the bride herself. The amount of mahr is not legally specified, however, moderation according to the existing social norm is recommended. The mahr may be paid immediately to the bride at the time of marriage, or deferred to a later date, or a combination of both. The deferred mahr however, falls due in case of death or divorce.

One matrimonial party expresses 'ijab" willing consent to enter into marriage and the other party expresses 'qubul" acceptance of the responsibility in the assembly of marriage ceremony. The contract is written and signed by the bride and the groom and their two respective witnesses. This written marriage contract ("Aqd-Nikah) is then announced publicly.

Allah says about Mahr in the Chapter `Woman' in Quran:
And give the women (on marriage) their Mahr as a free gift ...
Qur'an [4 : 4]

But if you had given the latter a cantar (of gold i.e. a great amount) for dower (Mahr) take not the least bit of it back ...
Qur'an [4 : 20]

Narrated Sahl bin Sa`d: " A woman came to the Prophet,, and presented herself to him (for marriage). He said, 'I am not in need of women these days.' Then a man said, 'O Allah's Apostle! Marry her to me." The Prophet asked him, 'What have you got?' He said, 'I have got nothing.' The Prophet said, 'Give her something, even an iron ring.' He said, 'I have got nothing.' The Prophet asked (him), "How much of the Quran do you know (by heart)?' He said, 'So much and so much.' The Prophet said, 'I have married her to you for what you know of the Quran.' '"
[Bukhari]