I borrowed a sum of money from my brother and we documented that in writing for preserving rights. After three months, he told me that he wanted to assess the value of that loan in gold(e.g. I borrowed from him an amount that equals 500 grams of gold), and that I should repay him in gold at the time of settlement(i.e. I should repay the value of 500 grams of gold at the time of settlement). You should pay attention to the fact that we haven`t agreed on this manner of repayment in the first place, so what is the ruling of Sharia in this regard ?
