What is the ruling on selling gold for US dollars on credit, with supporting evidence, and is it permissible for a فقيه (Islamic jurist) to rule that this is permissible both in cash and on credit due to the difference in their types?

It is not permissible to sell gold for US dollars on credit (deferred payment) due to the difference in their types while sharing the same underlying cause (being a medium of exchange/store of value). Hand-to-hand exchange is required at the time of the contract, based on the Hadith of 'Ubadah ibn al-Samit: "Gold for gold... hand-to-hand."