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 (nonmuslims). (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."
Sahih al-Bukhari Book 65, Hadith 174
← Previous Hadith Ibn `Umar came to us and a man said (to him), "What do you think about 'Qit-alal-Fitnah' (fighting caused by afflictions)." Ibn `Umar said (to him), "And do you understand what an affliction is? Muhammad used to fight against the pagans, and his fighting with them was an affliction, (and his fighting was) not like your fighting which is carried on for the sake of ruling."

Sahih al-Bukhari Book 65, Hadith 173 Next Hadith → When the Verse:--'If there are twenty steadfast amongst you (Muslims), they will overcome twohundred (non-Muslims).' was revealed, it became hard on the Muslims when it became compulsory that one Muslim ought not to flee (in war) before ten (non-Muslims). So (Allah) lightened the order by revealing: '(But) now Allah has lightened your (task) for He knows that there is weakness in you. So if there are of you one-hundred steadfast, they will overcome (two-hundred (non-Muslims).' (8.66) So when Allah reduced the number of enemies which Muslims should withstand, their patience and perseverance against the enemy decreased as much as their task was lightened for them.

Sahih al-Bukhari Book 65, Hadith 175