The comparison he made for his own message
The man in the story had nothing to show for it but his own eyes.
رَأَيْتُ الْجَيْشَ بِعَيْنَىَّ، وَإِنِّي أَنَا النَّذِيرُ الْعُرْيَانُ فَالنَّجَا النَّجَاءَ
Raʾaytu-l-jaysha bi-ʿaynayy, wa innī ana-n-nadhīru-l-ʿuryān, fa-n-najā-n-najāʾ
“I have seen the army with my own eyes, and I am the naked warner. Escape, escape.”
Where this comes from
A scout who has run so hard he has lost his clothes has no way to prove what he saw. Part of the people believed him and left quietly by night and were saved. Part called him a liar, and the army came upon them in the morning and wiped them out.
The full narration
Narrated Abu Musa:Allah's Messenger (ﷺ) said. "My example and the example of the message with which Allah has sent me is like that of a man who came to some people and said, "I have seen with my own eyes the enemy forces, and I am a naked warner (to you) so save yourself, save yourself! A group of them obeyed him and went out at night, slowly and stealthily and were safe, while another group did not believe him and thus the army took them in the morning and destroyed them
Source
Ṣaḥīḥ al-Bukhārī · 6482
- Agreed upon as authentic (al-Bukhārī / Muslim)