What is the ruling on using the term "abd" (slave) for people with dark skin, and is it permissible according to Sharia? And how should one respond to whoever says it?

It is forbidden to call a person with black skin "slave" (al-abd) because it involves derision and degradation. Allah has prohibited calling each other by offensive nicknames and harming or belittling a Muslim. Furthermore, the use of such words opens the door to enmity and hatred among Muslims. Whoever hears these nicknames must advise the one who utters them and warn him of their danger.