وَلِأَبِي دَاوُدَ: «مَنْ بَاعَ بَيْعَتَيْنِ فِي بَيْعَةٍ فَلَهُ أَوَكَسُهُمَا، أَوْ اَلرِّبَا»
“If anyone makes to transactions combined in one he is entitled to take the lower price, or (it is considered) usury.”
Bulugh al-Maram 912, Book 7, Business Transactions, Hadith 23. 1 min read