Praise be to Allaah.
If the couple agree on giving the mahr in a
currency other than that which is mentioned in the marriage contract, that
is permissible, so long as the exchange is done at the rate on the day on
which it is given, not the rate on the day of the contract, and the
equivalent amount is given in full; they should not separate when there is
still something outstanding that the husband has to pay.
The basic principle concerning that is the
report narrated by Abu Dawood (3354) and al-Nasaa’i (4582) from Ibn ‘Umar
(may Allaah be pleased with him) who said: I used to sell camels in
al-Baqee’, and I would sell them for dinars and take dirhams, and I would
sell them for dirhams and take dinars. I asked the Messenger of Allaah
(peace and blessings of Allaah be upon him) about that and he said: “There
is nothing wrong with taking the price of that day, so long as you do not
separate when there is still something to be paid.” Classed as saheeh by
al-Nawawi in al-Majmoo’ (9/330), Ibn al-Qayyim in Tahdheeb
al-Sunan, and Ahmad Shaakir in Tahqeeq al-Musnad (7/226). Classed
as da’eef (weak) by al-Albaani in Da’eef Abi Dawood. The hadeeth is
in accordance with shar’i principles on buying and selling and on riba
(usury), hence the fuqaha’ adopted it. See: al-Sharh al-Mumti’
The Standing Committee for Issuing Fatwas
was asked about a man who took a loan in French currency, and when he paid
it back, the lender asked him to pay it in Algerian currency.
It is permissible to pay it off in Algeria
in the same amount of French currency, or in the equivalent amount of
Algerian currency at the rate of exchange on the day when it is paid off,
provided that it is paid before separating. End quote.
Fataawa al-Lajnah al-Daa’imah
And Allaah knows best.