Jami` at-Tirmidhi 1667

Narrated Abu Salih, the Freed slave of Uthman : "I heard Uthman while on the Minbar saying: 'I did not inform you about a Hadith I had heard from the Messenger of Allah (ﷺ), out of dismay that you might part from me. Then it occurred to me that I should narrate to you so that one may choose from these matters accordingly. I heard the Messenger of Allah (ﷺ) saying: "(Ribat) Guarding the frontier for a day in Allah's cause is beter in status than thousand days doing other than that.'" [Abu 'Eisa said:] This Hadith is Hasan Sahih Gharib. Muhammad bin Ism'ail said: "Abu Salih, the freed slave of 'Uthman's name is Burkan