Some men from the companions of the Messenger of Allah ﷺ asked, "Messenger of Allah, who are these people Allah has mentioned, that if we turn away, He will replace us with others who will not be like us?"Salman was sitting beside the Messenger of Allah ﷺ. The Messenger of Allah ﷺ tapped Salman's thigh and said, "This man and his people. By the One in whose hand is my soul, if faith were suspended at the Pleiades, Some men from Persia would reach it."
حدثنا علي بن حجر أنبأنا إسمعيل بن جعفر حدثنا عبد الله بن جعفر بن نجيح عن العلاء بن عبد الرحمن عن أبيه
قال ناس من أصحاب رسول الله ﷺ يا رسول الله من هؤلاء الذين ذكر الله إن تولينا استبدلوا بنا ثم لم يكونوا أمثالنا قال وكان سلمان بجنب رسول الله ﷺ قال فضرب رسول الله ﷺ فخذ سلمان وقال هذا وأصحابه والذي نفسي بيده لو كان الإيمان منوطا بالثريا لتناوله رجال من فارس
Grading, hasan. It was also narrated by Muslim bin Khalid Zanji, from Ala bin Abdul-Rahman, with the same wording (Tafsir Tabari 26/42, and Sahih Ibn Hibban [al-Ihsan] 7979), and Ismail bin Jafar followed them both in narrating it (Dalail Nubuwwah by Bayhaqi 6/334).The hadith also has many corroborating narrations in Bukhari, hadith nos. 4897 and 4898, and elsewhere.