Tawus bin Kaysan طاوس · The Book of Financial Transactions

" The Messenger of Allah ruled that what a slave earns belongs to his guarantor."

"The messenger of Allah forbade two kinds of transactions: Mulamash and Mumabadha."

he did not like to exchange Dinars for Dirhams or Dirhams for Dinars.

he did not see anything wrong with it even if it was on credit.

This is what I have found on this topic.

"I came to the Prophet and said: 'Wait, I want to ask you something. I sell camels in Al-Baqi with a price set in Dinars but I accept Dirhams instead.' He said: 'There is nothing wrong with it if you take the price on that day, still unfinished business between you both (buyer and seller)"'

"When the Prophet (ﷺ) came to Al-Madinah, he called for a scale and weighed (something) for me and gave me more."