Kaab bin Ujra reported,
The Messenger of Allah ﷺ mentioned a tribulation, describing it as imminent and grave. Then a man passed by, wrapped in a cloak covering his head. The Prophet ﷺ said, "This man on that day will be upon the truth."So I rushed off, or he said hurried, and took hold of the man by his upper arms and said, "This one, Messenger of Allah?"He replied, "This one." And there he was, Uthman bin Affan 
.
Ahmad 18118
Sahihحدثنا إسحاق بن سليمان الرازي أخبرني مغيرة بن مسلم عن مطر الوراق عن ابن سيرين
عن كعب بن عجرة قال
ذكر رسول الله ﷺ فتنة فقربها وعظمها قال ثم مر رجل متقنع في ملحفة فقال هذا يومئذ على الحق فانطلقت مسرعا أو قال محضرا فأخذت بضبعيه فقلت هذا يا رسول الله قال هذا فإذا هو عثمان بن عفان رضي الله عنه
Its isnad is sahih. Its narrators are reliable, though there is some discussion about a few of them. Matar Warraq is Ibn Tahman. There has been discussion about his memory, but his hadith is hasan due to corroborating evidence, and his hadith appears in Muslim, as does that of Mughira bin Muslim Qasmali. There is also some discussion about whether Ibn Sirin heard directly from Kaab bin Ujra. However, the hadith has already appeared at 17986 and 17982, so see its references there.