Regarding Surat Al-Haqqah Jami` at-Tirmidhi 3321

Arabic hadith text
حَدَّثَنَا يَحْيَى بْنُ مُوسَى، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ عَبْدِ اللَّهِ بْنِ سَعْدٍ الرَّازِيُّ، وَهُوَ الدَّشْتَكِيُّ أَنَّ أَبَاهُ، أَخْبَرَهُ أَنَّ أَبَاهُ رَحِمَهُ اللَّهُ أَخْبَرَهُ كَذَا، قَالَ أَخْبَرَهُ قَالَ رَأَيْتُ رَجُلاً بِبُخَارَى عَلَى بَغْلَةٍ وَعَلَيْهِعِمَامَةٌ سَوْدَاءُ وَيَقُولُ كَسَانِيهَا رَسُولُ اللَّهِ صلى الله عليه وسلم ‏.‏
Translation
Abdur-Rahman bin Abdullah bin Sa’d Ar-Razi [and he is Ad-Dashtaki] narrated

that his father informed him, that his father – may Allah have mercy upon him – informed him, he said: “I saw a man in Bukhara upon a mule wearing a black Imamah, saying: ‘It was given to me by the Messenger of Allah.’”