Abdullah bin Abbas reported,

When the verse "If there are twenty steadfast among you, they will overcome two hundred" [Anfal 8:65] was revealed, it weighed heavily on the Muslims, since it made it obligatory for them that no single man flee from ten. Then relief came, and Allah said, "Now Allah has lightened it for you, knowing that there is weakness among you. So if there are a hundred steadfast among you, they will overcome two hundred" [Anfal 8:66].He said, "When Allah lightened their obligation regarding the numbers, He also reduced what was required of their steadfastness in proportion to the relief He had granted them."

Azami 12411

Sahih

عن ابن عباس قال

لما نزلت{إن يكن منكم عشرون صبرون يغلبوا مائتين}، شق ذلك على المسلمين حين فرض عليهم أن لا يفر واحد من عشرة، فجاء التخفيف، فقال: {الآن خفف الله عنكم وعلم أن فيكم ضعفا فإن يكن منكم مائة صابرة يغلبوا مائتين} قال: فلما خفف الله عنهم من العدة، نقص من الصبر بقدر ما خفف عنهم.

الأعظمي 12411صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Tafsir of the great Quran
Chapter
Virtues of Surah Baqarah
Section
His saying, "O Prophet, urge the believers to fight. If there are among you twenty steadfast ones, they will overcome two hundred; and if there are among you a hundred, they will overcome a thousand of those who disbelieve, because they are a people who do not understand. Now Allah has lightened your burden, for He knows that there is weakness in you. So if there are among you a hundred steadfast ones, they will overcome two hundred; and if there are among you a thousand, they will overcome two thousand by the permission of Allah. And Allah is with the steadfast."
Numbering
Jami al-Kamil 12411 (2nd edition)
Azami 12411