Narrated by Abdullah bin Abbas (may Allah be pleased with them both): The Prophet (peace and blessings of Allah be upon him) said:“Whoever buys grain should not sell it until he has taken possession of it.”__QUR_N__ Ibn Abbas (may Allah be pleased with them both) said: I consider everything to be like grain in this regard. __XREF_N__ Imam Tirmidhi says:
1- The hadith of Ibn Abbas (may Allah be pleased with them both) is Hasan Sahih.
2- In this chapter, there are also ahadith from Jabir, Ibn Umar, and Abu Hurairah (may Allah be pleased with them all).
3- Most of the people of knowledge act upon this; they have declared it impermissible to sell grain until the buyer has taken possession of it.
4- And some of the people of knowledge have permitted selling before possession for one who buys something that is neither measured nor weighed, nor eaten or drunk.
5- According to the people of knowledge, the strictness is regarding grain. This is also the view of Ahmad and Ishaq bin Rahwayh. __REF_N__