Musannaf Ibn Abi Shaybah

Hazrat Umar bin Abdul Aziz (may Allah have mercy on him) said that whoever sold a slave who was prohibited from trade, he has wasted his wealth.

Ibrahim (may Allah have mercy on him) said that when the master comes to the people of the market and informs them that he has prohibited his slave from trading, then it is not permissible for anyone to conduct transactions with him.

Hasan (may Allah have mercy on him) says that if a person prevents a slave in the market from transacting or doing anything in front of the people of the market, then it is not permissible to buy or sell with him.

Hazrat Ibn Sirin (may Allah have mercy on him) did not consider being prevented from trade to be of any significance.

It is narrated from Hazrat Bakr Al-Anazi (may Allah have mercy on him) that a man forbade his slave from trading. The slave took the matter to Hazrat Ali (may Allah be pleased with him). Hazrat Ali (may Allah be pleased with him) asked the owner, "Do you give him dirhams and send him to buy meat and such things?" He replied, "Yes." Upon hearing this, Hazrat Ali (may Allah be pleased with him) permitted the slave to engage in trade.