قَالَ مَالِكٌ : وَكُلُّ شَيْءٍ يَنْتَفِعُ بِهِ النَّاسُ مِنَ الْأَصْنَافِ كُلِّهَا، وَإِنْ كَانَتِ الْحَصْبَاءَ وَالْقَصَّةَ، فَكُلُّ وَاحِدٍ مِنْهُمَا بِمِثْلَيْهِ إِلَى أَجَلٍ فَهُوَ رِبًا، وَوَاحِدٌ مِنْهُمَا بِمِثْلِهِ وَزِيَادَةُ شَيْءٍ مِنَ الْأَشْيَاءِ إِلَى أَجَلٍ فَهُوَ رِبًا.
Imam Malik, may Allah have mercy on him, said that as for things which are used, such as sand and lime, if they are sold for the same kind on deferred payment, whether equal or unequal, it is not permissible. If they are sold for cash, then it is permissible even if they are unequal.