We were sitting with the Prophet ﷺ when Surah al-Jumuah was revealed to him. When he recited "And others among them who have not yet joined them" [Jumuah 62:3], someone asked, "Who are these people, Messenger of Allah?"The Prophet ﷺ did not answer him until he had asked once, twice, or three times. Salman Farsi was among us. The Prophet ﷺ then placed his hand on Salman and said, "If faith were at the Pleiades, Some men from these people would still reach it."
حدثنا قتيبة حدثنا عبد العزيز عن ثور عن أبي الغيث
كنا جلوسا عند النبي ﷺ إذ نزلت عليه سورة الجمعة فلما قرأ {وآخرين منهم لما يلحقوا بهم} قال من هؤلاء يا رسول الله فلم يراجعه ﷺ حتى سأله مرة أو مرتين أو ثلاثا وفينا سلمان الفارسي قال فوضع النبي ﷺ يده على سلمان وقال لو كان الإيمان عند الثريا لناله رجال من هؤلاء
Its isnad is sahih. Bukhari reported it 6/189 in tafsir, chapter of Jumuah, "and others among them who have not yet joined them", and Muslim 4/1972 no. 2546 in the virtues of the companions, the virtue of Faris, and Tirmidhi 5/413 no. 3310 similarly to Bukhari.