The Messenger of Allah ﷺ said, "It is not lawful for a Muslim to shun another Muslim for more than three nights. As long as they remain in their estrangement, they are both deviating from the truth. The first of them to return will have his initiative serve as expiation for him. If he greets the other with peace and his greeting is not accepted and not returned, the angels return the greeting to him and Satan returns the greeting to the other. And if they both die in their state of estrangement, they shall never enter Paradise together."
قال حدثنا محمد بن جعفر قال حدثنا شعبة عن يزيد الرشك عن معاذة
قال رسول الله ﷺ لا يحل لمسلم أن يهجر مسلما فوق ثلاث ليال فإنهما ناكبان عن الحق ما داما على صرامهما وأولهما فيئا يكون سبقه بالفيء كفارة له وإن سلم فلم يقبل ورد عليه سلامه ردت عليه الملائكة ورد على الآخر الشيطان وإن ماتا على صرامهما لم يدخلا الجنة جميعا أبدا
Its isnad is sahih, but the first narration is more precise, and perhaps the one who preserved it precisely was Rawh, because his statement, "They will never be together in Paradise," is closer to the sound principles than "They will not [both] enter Paradise," since usually one of them is correct and the other is being obstinate, as the context indicates.