The Quran

إِلّا تَنصُروهُ فَقَد نَصَرَهُ اللَّهُ إِذ أَخرَجَهُ الَّذينَ كَفَروا ثانِيَ اثنَينِ إِذ هُما فِي الغارِ إِذ يَقولُ لِصاحِبِهِ لا تَحزَن إِنَّ اللَّهَ مَعَنا ۖ فَأَنزَلَ اللَّهُ سَكينَتَهُ عَلَيهِ وَأَيَّدَهُ بِجُنودٍ لَم تَرَوها وَجَعَلَ كَلِمَةَ الَّذينَ كَفَرُوا السُّفلىٰ ۗ وَكَلِمَةُ اللَّهِ هِيَ العُليا ۗ وَاللَّهُ عَزيزٌ حَكيمٌ

Muhammad Asad

If you do not succour the Apostle,¹ then [know that God will do so -just as] God succoured him at the time when those who were bent on denying the truth drove him away, [and he was but] one of two:² when these two were [hiding] in the cave, [and] the Apostle said to his companion, "Grieve not: verily, God is with us."³ And thereupon God bestowed upon him from on high His [gift of] inner peace,⁴ and brought utterly low the cause of those who were bent on denying the truth, whereas the cause of God remained supreme:⁵ for God is almighty, wise.

Lit., "him", i.e., Muhammad.
Lit., "the second of two": an allusion to the Prophet's flight, in the company of Abu Bakr, from Mecca to Medina in the year 622 of the Christian era. The expression "the second of two" does not imply any order of precedence but is synonymous with "one of two": cf. the Prophet's saying to Abu Bakr, on that very occasion, "What [could], in thy opinion, [happen] to two [men] who have God as the third with them?" (Bukhari, in the chapter Fada'il Ashab an-Nabi)
When the Prophet and Abu Bakr left on their hijrah to Medina, they first hid for three nights in a cave on Mount Thawr, in the vicinity of Mecca, where they were almost discovered and apprehended by the pagan Quraysh who were pursuing them (Bukhari, loc. cit.).
Cf. verse 26 above.
Lit., "is the highest". The expression rendered by me as "cause", which occurs twice in this sentence, reads, literally, "word" (kalimah).