The Messenger of Allah ﷺ as saying: If anyone buys grain, he should not sell it until he measures it. Abu Bakr added in his version: I asked Ibn 'Abbas: Why ? He replied: Do you not see that they sell (grain) for gold, but the grain is still with the seller.
قَالَ رَسُولُ اللَّهِ ﷺ مَنِ ابْتَاعَ طَعَامًا فَلاَ يَبِعْهُ حَتَّى يَكْتَالَهُ زَادَ أَبُو بَكْرٍ قَالَ قُلْتُ لاِبْنِ عَبَّاسٍ لِمَ قَالَ أَلاَ تَرَى أَنَّهُمْ يَتَبَايَعُونَ بِالذَّهَبِ وَالطَّعَامُ مُرَجًّى
He who buys foodgrain should not sell it, until he has weighed it (and then taken possession of it). I (Tawus) said to Ibn Abbas (Allah be pleased with them): Why is it so? Thereupon he said: Don't you see that they (the people) sell foodgrains against gold for the stipulated time. Abu Kuraib did not make any mention of the stipulated time.
قَالَ رَسُولُ اللَّهِ ﷺ مَنِ ابْتَاعَ طَعَامًا فَلاَ يَبِعْهُ حَتَّى يَكْتَالَهُ فَقُلْتُ لاِبْنِ عَبَّاسٍ لِمَ فَقَالَ أَلاَ تَرَاهُمْ يَتَبَايَعُونَ بِالذَّهَبِ وَالطَّعَامُ مُرْجَأٌ وَلَمْ يَقُلْ أَبُو كُرَيْبٍ مُرْجَأٌ
The Prophet ﷺ said, "He who buys foodstuff should not sell it till he has received it." (Using translation from Bukhārī 2133)
قَالَ رَسُولُ اللهِ ﷺ مَنِ ابْتَاعَ طَعَامًا فَلَا يَبِعْهُ حَتَّى يَقْبِضَهُ قُلْتُ لِابْنِ عَبَّاسٍ لِمَ؟ قَالَ أَلَا تَرَى أَنَّهُمْ يَتَبَايَعُونَ بِالذَّهَبِ وَالطَّعَامُ مُرْجَأٌ