Al-Imran: 13
"There has already been for you a sign in two parties that met: one party fighting in the way of Allah, and another disbelieving, seeing them as twice their number by [the] eye's sight. And Allah supports with His victory whom He wills. Indeed, in that is a lesson for those of vision."
"There has already been for you a sign"
The address is to the polytheists of Quraysh.
"In two parties that met"
On the day of Badr.
"Seeing them as twice their number"
The polytheists saw the Muslims as twice the number of the polytheists—nearly two thousand. Or, they saw them as twice the number of the Muslims themselves (six hundred and some odd). Allah showed them to the polytheists—despite their small number—as many times their size, so that they would fear them and be cowardly about fighting them. This was a reinforcement for them from Allah, just as He reinforced them with the angels.
The evidence for this is the recitation of Nafi‘: (tarawnahum) with a ta’ (you see), meaning: "O polytheists of Quraysh, you see the Muslims as twice your disbelieving party, or twice their own number."
If you ask: "This contradicts His saying in Surah al-Anfal: 'And He made you appear few in their eyes' (8:44)," I say: They were made to appear few at first so that they would be emboldened to attack them. Then, when they met, they were made to appear many in their eyes until they were overcome. Thus, the reduction and the multiplication occurred at two different times.
A parallel to this, where matters are interpreted based on differing circumstances, is His saying: "So on that Day, neither man nor jinn will be asked about his sin" (55:39), and His saying: "And stop them; indeed, they are to be questioned" (37:24). The reduction of them at one time and their multiplication at another in their eyes is more eloquent in demonstrating power and manifesting the sign.
It is also said: The Muslims saw the polytheists as twice the number of the Muslims, based on the command established for them to resist one against two, in His saying: "If there are among you one hundred who are steadfast, they will overcome two hundred" (8:65), after they were tasked with one resisting ten in His saying: "If there are among you twenty who are steadfast, they will overcome two hundred" (8:65). For this reason, their weakness was described as "fewness," because it was few in relation to the ten-fold requirement, and the disbelievers were three times their number. However, the recitation of Nafi‘ does not support this. Ibn Musarrif recited (yurawnahum) in the passive voice with a ya’ and ta’, meaning: Allah shows them that by His power.
(Fi’atin tuqatilu wa-ukhra kafira) was recited in the genitive case as an appositive (badal) to fi’atayn, and in the accusative case as a specification (ikhtisas) or as a state (hal) from the pronoun in iltaqata.
"By the eye's sight"
Meaning: a manifest, clear vision, without ambiguity, a direct witnessing like all other direct witnessings.
"And Allah supports with His victory"
Just as He supported the people of Badr by making them appear many in the eyes of the enemy.
"Beautified for the people is the love of desires—of women and sons, and heaped-up sums of gold and silver, and fine branded horses, and cattle and tilled land. That is the enjoyment of worldly life, while Allah has with Him the best return. Say, 'Shall I inform you of [something] better than that? For those who fear Allah will be gardens in the presence of their Lord beneath which rivers flow, wherein they abide eternally, and purified spouses and approval from Allah. And Allah is Seeing of [His] servants—Those who say, "Our Lord, indeed we have believed, so forgive us our sins and protect us from the punishment of the Fire"—The patient, the truthful, the devout, those who spend [in the way of Allah], and those who seek forgiveness before dawn.'" (14-17)