مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2900
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
Ibn 'Abbas said: The Messenger of Allah (ﷺ) said: "Any man who claims to belong to someone other than his father or to someone other than his former masters who manumitted him, upon him be the curse of Allah, the angels and all the people until the Day of Resurrection, and no obligatory or nafl act of worship will be accepted from him.”
Musnad Ahmad 2921A saheeh hadeeth, this is a da’eef isnad]