Musnad Ahmad 8:66

Isma'il ibn Ibrahim narrated to us, 'Asim al-Ahwal narrated to us, from Abu 'Uthman al-Nahdi, who said: Sa'd said—and once he said: I heard Sa'd—saying: My two ears heard it and my heart retained it from Muhammad, may Allah bless him and grant him peace: "Whoever claims a father other than his own father, while he knows that he is not his father, then Paradise is forbidden to him." He said: So I met Abu Bakrah and told him [about it], and he said: My two ears also heard it and my heart retained it from Muhammad, may Allah bless him and grant him peace.