Abdullah bin Abbas reported,

That is, by "the Criterion" he means the day of Badr, the day on which Allah distinguished between truth and falsehood.

Azami 12395

Hasan

في قوله عزوجل: {إن كنتم ءامنتم بالله وما أنزلنا على عبدنا يوم الفرقان}

عن ابن عباس قال

يعني بالفرقان يوم بدر يوم فرق الله بين الحق والباطل.

الأعظمي 12395حسن
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Tafsir of the great Quran
Chapter
Virtues of Surah Baqarah
Section
His saying, "And know that whatever you obtain of war booty, then indeed for Allah is one fifth of it and for the Messenger and for near relatives and the orphans and the needy and the traveler, if you have believed in Allah and in what We sent down to Our servant on the day of criterion, the day when the two armies met. And Allah is over all things competent"
Numbering
Jami al-Kamil 12395 (2nd edition)
Azami 12395