ibn Abbas · The Book of Musaqah

The slave of Banu Bayada cupped Allah's Apostle (ﷺ) and he gave him his wages, and talked to his master and he reduced the charges, and if this earning was unlawful Allah's Apostle (ﷺ) would not have given it.

This news reached 'Umar that Samura had sold wine, whereupon he said: May Allah destroy Samura; does he not know that Allah's Messenger (ﷺ) said:" Let there be the curse of Allah upon the Jews that fat was declared forbidden for them, but they melted it and then sold it"?

There is no element of interest when the money or commodity is exchanged hand to hand.

Those who pay in advance for anything must do so for a specified weight and for a definite time.

He who makes an advance payment should not make advance payment except for a specified measure and weight (and for a specified period).