Mishkat al-Masabih 11 Business Transactions كتاب البيوع 84

وَعَنِ ابْنِ عَبَّاسٍ قَالَ: أَمَّا الَّذِي نَهَى عَنْهُ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَهُوَ الطَّعَامُ أَنْ يُبَاعَ حَتَّى يُقْبَضَ. قَالَ ابْنُ عَبَّاسٍ: وَلَا أَحْسِبُ كُلَّ شَيْءٍ إِلاَّ مثلَه

Ibn ‘Abbas said what the Prophet forbade was that grain should be sold before it had been received. Ibn ‘Abbas said, “I do not think this applies to every commodity, but only to things of that type.” (Bukhari and Muslim.)