The Quran

وَما أَرسَلنا مِن رَسولٍ إِلّا بِلِسانِ قَومِهِ لِيُبَيِّنَ لَهُم ۖ فَيُضِلُّ اللَّهُ مَن يَشاءُ وَيَهدي مَن يَشاءُ ۚ وَهُوَ العَزيزُ الحَكيمُ

Muhammad Asad

AND NEVER have We sent forth any apostle otherwise than [with a message] in his own people's tongue, so that he might make [the truth] clear unto them;¹ but God lets go astray him that wills [to go astray], and guides him that wills [to be guided] - for He alone is almighty, truly wise.²

Since every divine writ was meant to be understood by man, it is obvious that each had to be formulated in the language of the people whom the particular prophet was addressing in the first instance; and the Qur'an - notwithstanding its universal import (cf. note 126 on 7:158) - is no exception in this respect.
Or: "God lets go astray whomever He wills, and guides whomever He wills". All Qur'anic references to God's "letting man go astray" must be understood against the background of 2:26-27 - "none does He cause to go astray save the iniquitous, who break their bond with God" (regarding which latter expression, see surah 2, note 19): that is to say, man's "going astray" is a consequence of his own attitudes and inclinations and not a result of an arbitrary "predestination" in the popular sense of this word (cf. surah 2, note 7). In his commentary on the above verse, Zamakhshari stresses this aspect of free choice on the part of man and points out that "God does not cause anyone to go astray except one who, as He knows, will never attain to faith; and He does not guide anyone aright except one who, as He knows, will attain to faith. Hence, the [expression] 'causing to go astray' denotes [God's] leaving [one] alone (takhliyah) and depriving [him] of all favour, whereas [the expression] 'guidance' denotes [His] grant of fulfilment (tawfiq) and favour.... Thus, He does not forsake anyone except those who deserve to be forsaken, and does not bestow His favour upon anyone except those who deserve to be favoured." Commenting on the identical phrase occurring in 16:93, Zamakhshari states: "[God] forsakes him who, as He knows, will [consciously] choose to deny the truth and will persevere in this [denial]; and ... He bestows His favour upon him who, as He knows, will choose faith: which means that He makes the issue dependent on [man's] free choice (al-ikhtiyar), and thus on his deserving either [God's] favour or the withdrawal of [His] aid ... and does not make it dependent on compulsion [i.e., predestination], which would rule out [man's] deserving anything of the above."