I arrived in Madinah and we received news that the plague had broken out in Kufa.I asked, "Who narrates this hadith?"It was said, "Amir bin Saad," but he was away at the time.I then met Ibrahim bin Saad, who told me that he heard Usama bin Zayd relating to Saad that the Messenger of Allah ﷺ said, "When the plague breaks out in a land, do not enter it, and if it breaks out while you are there, do not leave it."I asked him, "Did you yourself hear this from Usama?"He replied, "Yes."
حدثنا بهز حدثنا شعبة أخبرني
قدمت المدينة فبلغنا أن الطاعون وقع بالكوفة قال فقلت من يروي هذا الحديث فقيل عامر بن سعد قال وكان غائبا فلقيت إبراهيم بن سعد فحدثني أنه سمع أسامة بن زيد يحدث سعدا أن رسول الله ﷺ قال إذا وقع الطاعون بأرض فلا تدخلوها وإذا وقع وأنتم بها فلا تخرجوا منها قال قلت أنت سمعت أسامة قال نعم
Its isnad is sahih. Bahz is Ibn Asad Al-Ammi, who is trustworthy. Ahmad said, "He represents the ultimate standard in precision." Ibrahim bin Saad bin Abu Waqqas is a trustworthy successor (tabii).This hadith here is from the musnad of Usama bin Zayd, which he related to Saad, and Saad also used to narrate it, as has passed several times at 1491, 1508, and 1527. Bukhari related it in Al-Kabir 1/1/288 through the route of Shubah with this same isnad. He then related it through the route of Amash, from Habib, from Ibrahim, from Usama and Saad, as a raised hadith (marfu). He then related it through the route of Sufyan, from Habib, from Ibrahim, from Usama bin Zayd and Khuzayma bin Thabit, as a raised hadith (marfu).