Bulugh al-Maram 7 Business Transactions كتاب البيوع 23

وَلِأَبِي دَاوُدَ: { مَنْ بَاعَ بَيْعَتَيْنِ فِي بَيْعَةٍ فَلَهُ أَوَكَسُهُمَا, أَوْ اَلرِّبَا } 1 . 1 – حسن. رواه أبو داود ( 3460 ).

Abu Dawud has: “If anyone makes to transactions combined in one he is entitled to take the lower price, or (it is considered) usury.”