Fairness in Expenditure on Two Wives

Question :

I request a legal verdict for one who has two wives, one of them in Riyadh and the other in Sudan, regarding expenditure on them, since the expenditure upon the first, who lives in Riyadh in spite of her having only a few children is three times as much as is spent on the second wife in Sudan, although she has many children. The reason for this is due to the economic situation and the currency regulations in every country. So the expenditure upon the one who lives in Riyadh is about 1,500 Riyals and the expenditure upon the one who lives in Sudan is about 500 Riyals. Advise me how can I be fair in matters of expenditure, and may Allah reward you with goodness.

Answer:

It is incumbent upon the husband to spend on each of his wives that which is sufficient in her location, to provide what is customary, such as food, drink clothing and other related things. And if one of them has more children, her allowance must be increased accordingly, taking care to be just in everything, according to the Words of Allah, Most High:
"but the father of the child shall bear the cost of the mother's food and clothing on a reasonable basis."

and the words of the Prophet in his sermon during the Farewell Pilgrimage:
"And it is their right upon you that you bear the cost of their sustenance and their clothing on a reasonable basis."

And Allah is the Granter of success.

Source:
Ibn Baz
Fatawa Islamiyah, Vol. 5 Pages 360-361