The Book of the Believer · Hadith 175 (#Ḥadīth #5)
Chapter 8 | What Allah (azwj) has Forbidden a Believer to do Against a Fellow Believer
175 - وعن أبي عبد الله عليه السلام أنه قال: لو قال الرجل لأخيه أف لك انقطع ما بينهما، قال، فإذا قال له: أنت عدوي فقد كفر أحدهما، فإن اتهمه انماث الايمان في قلبه، كما ينماث الملح في الماء.
175. It has been reported that Abu 'Abd Allah said: If a person says to his brother the lease expression of contempt, he cut off any relation between them; and if he says to him, 'you are my enemy,' one of them has then committed apostasy; and if he accuses him falsely, faith will dissolve in his heart like salt in water.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).