"The Messenger of Allah (ﷺ) cursed the one who separates a mother and her child, or a brother from his brother."
Sunan Ibn Majah Book 12, Hadith 114
← Previous Hadith "The Messenger of Allah (ﷺ) gave me two slaves who were brothers, and I sold one of them. He said: 'What happened with the two slaves?' I said: 'I sold one of them.' He said: 'Take him back."'

Sunan Ibn Majah Book 12, Hadith 113 Next Hadith → "Adda' bin Khalid bin Hawdhah said to me: 'Shall I not read to you a letter that the Messenger of Allah (ﷺ), wrote to me?' I said: 'Yes.' So he took out a letter. In it was: 'This is what 'Adda' bin Khalid bin Hawdhah bought Muhammad the Messenger of Allah (ﷺ) He bought from him a slave' or 'a female slave, having no ailments, nor being a runaway, not having any malicious behavior. Sold by a Muslim to a Muslim.'"

Sunan Ibn Majah Book 12, Hadith 115