Muqaddam bin Maadi Kareeb had a slave girl who used to sell milk, and Miqdam would collect the payment. Someone said to him, "Glory be to Allah, do you sell milk and take the payment yourself?"He replied, "Yes, and there is nothing wrong with that. I heard the Messenger of Allah ﷺ say, 'A time will surely come upon people when nothing will be of use except the dinar and the dirham.'"
حدثنا أبو اليمان قال حدثنا
كانت لمقدام بن معدي كرب جارية تبيع اللبن ويقبض المقدام الثمن فقيل له سبحان الله أتبيع اللبن وتقبض الثمن فقال نعم وما بأس بذلك سمعت رسول الله ﷺ يقول ليأتين على الناس زمان لا ينفع فيه إلا الدينار والدرهم
No references are available.
Its chain of transmission is daif, because of Abu Bakr bin Abu Maryam, whom they graded daif due to his confusion in old age, and Haythami said likewise in 4/64.