He mentioned a hadith he had narrated from the Prophet ﷺ which I had not heard him narrate any other hadith from the Prophet ﷺ besides it. The Prophet ﷺ said, "Whoever Allah wishes good for, He grants him understanding of the religion. A group of the Muslims will continue to fight for the truth, prevailing over those who oppose them, until the Day of Resurrection."
حدثنا كثير بن هشام قال حدثنا جعفر حدثنا يزيد بن الأصم قال سمعت
ذكر حديثا رواه عن النبي ﷺ لم أسمعه روى عن النبي ﷺ حديثا غيره أن النبي ﷺ قال من يرد الله به خيرا يفقه في الدين ولا تزال عصابة من المسلمين يقاتلون على الحق ظاهرين على من ناوأهم إلى يوم القيامة
Its isnad is sahih. Kathir bin Hisham is Kullabi, deemed reliable by Ibn Main, Ajli, Ibn Saad, and others. Jafar is Ibn Burqan Kullabi, deemed trustworthy, and his hadith appears in Muslim. Yazid bin Asam Kinaii is reliable and firmly established, and it is said that he had seen the Prophet. Both parts of it were narrated by Muslim, 3/1524, no. 1037m, and Bukhari narrated something similar to it in 13/293, no. 7312, Fath.