´Abu Zubair narrated that he heard Jabir bin 'Abdullah say:` "The Prophet said: ' A heap of grain should not be sold for a heap of grain, or for a heap of grain of known measure. "
Hadith Referenceسنن نسائي / كتاب البيوع / 4552
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:حسن
Hadith Takhrij«انظر ما قبلہ (صحیح)»
Brief Explanation
1؎: Because the quantity of both is not known, it is possible that one may be more and the other less, whereas disparity (increase or decrease) is not permissible.
2؎: Because although the quantity of one pile is known, the other is not, so it is possible that there may be an increase or decrease, which is not permissible. This applies in the case when both piles are of the same kind.
Explanation & Benefits
Hafiz Muhammad Ameen
This prohibition applies when the grain on both sides is of the same type, because in such a case, it is forbidden to transact with any increase or decrease. If the type changes, for example: wheat on one side and dates or something else on the other, then an increase or decrease is permissible. Likewise, at that time, there is no harm in buying and selling measured or unspecified grain. However, the condition is that this transaction must be hand to hand. Deferred payment is not permissible.
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 4552