Is it correct to say that the Messenger Muhammad, may God’s prayers and peace be upon him, said to Ali ibn Abi Talib, may God be pleased with him: "O Ali, the seller is Gabriel and the buyer is Michael," this being in the context of a story about selling a she-camel after Ali had given six dirhams in charity?

The story mentioned about Ali ibn Abi Talib has no basis or chain of narration (isnad). Al-Safuri mentioned it in "Nuzhat al-Majalis" without an isnad. When Al-Suyuti was asked about it, he replied that it is among the fabricated lies, and it is highly probable that it was fabricated by storytellers (qussas) or the Rawafid. The virtues of Ali are numerous and well-established, not needing such fabricated tales. The reward for the one who gives charity and Allah's compensation for it are affirmed in the Quran and Sunnah. Allah Almighty said: "And whatever you spend of anything, He will compensate it; and He is the best of providers." (Surat Saba, 34:39). The Prophet, peace and blessings be upon him, said: "O Allah, grant compensation to the one who spends." So, there is no need for such fabricated stories.