It is not permissible to buy a product then sell it when it is still in the warehouse of the first vendor, before it has been moved
Question

Some traders buy a product then they do not take possession of it or check it, rather they take a receipt which shows that they have paid for it and it is now theirs, and they leave it in the warehouse of the first vendor from whom they bought it. Then the second vendor sells it to someone else, whilst it is still in the storehouse of the first vendor. What is the ruling on that?.
Praise be to Allah.It is not permissible for the purchaser of this product to sell it so long as it is still in the possession of the seller, until the purchaser has taken possession of it and moved it to his house or the marketplace, because of the saheeh ahadith that have been narrated from the Prophet (peace and blessings of Allah be upon him) concerning that. For example, he (peace and blessings of Allah be upon him) said: “It is not permissible to sell something on condition that the purchaser lend you something, and it is not permissible to have two conditions in one transaction, and no profit is permissible unless possession has been taken of the goods, and you cannot sell what is not in your possession.” Narrated by Ahmad and the authors of al-Sunan with a saheeh isnaad. 
And he (peace and blessings of Allah be upon him) said to al-Hakeem ibn Hizaam: “Do not sell that which you do not have.” Narrated by the five except Abu Dawood, with a jayyid isnaad.  
And it was narrated from Zayd ibn Thaabit (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) forbade selling a product in the place where it was bought until the merchants have taken possession of it and moved it to their own property. Narrated by Ahmad and Abu Dawood; classed as saheeh by Ibn Hibbaan and al-Haakim. 
Similarly, if a person buys from the purchaser, it is not permissible for him to sell it until he transfers it to his house or to another place in the marketplace, because of the ahadith quoted and other ahadith which convey the same meaning. And Allah is the Source of strength.