Is it permissible to sell a commodity that I do not own by proposing a price lower than what is offered, then sell it at a higher price after purchasing it?

It is permissible to sell a phone after purchasing and taking possession of it. However, selling it before acquiring it and completing its purchase from the first owner is not permissible, due to the Prophet's (peace be upon him) prohibition of selling what one does not own, and his prohibition of selling what one has bought until one takes possession of it and receives it in full. Authentic hadiths have indicated the prohibition of selling goods where they are bought until merchants transport them to their own places.