Sahih Bukhari | Volume 6 | Hadith Number 175

Narrated by Ibn Abbas
When the Verse: "If there are twenty steadfast amongst you, they will overcome two hundred." (8:65) was revealed, then it became obligatory for the Muslims that one (Muslim) should not flee from ten (non-Muslims). Sufyan (the sub-narrator) once said, "Twenty (Muslims) should not flee before two hundred (non Muslims)." Then there was revealed: 'But now Allah has lightened your (task)...' (8:66)

So it became obligatory that one-hundred (Muslims) should not flee before two hundred (non-Muslims). (Once Sufyan said extra, "The Verse: 'Urge the believers to the fight. If there are twenty steadfast amongst you (Muslims)...' was revealed.) Sufyan said, "Ibn Shabrama said, "I see that this order is applicable to the obligation of enjoining good and forbidding evil."