It was narrated that Abu ‘Uthman an-Nahdi said: Sa"d said - and on one occasion he said: I heard Sa"d say :

My ears heard and my heart understood from Muhammad (ﷺ) that “whoever claims to belong to a father other than his father, knowing that he is not his father, Paradise will be forbidden to him." He said: “I met Abu Bakrah and told it to him, and he said: And my ears also heard it and my heart understood it from Muhammad (ﷺ).”