وَقَالَ ٱلَّذِينَ كَفَرُوا۟ لَوْلَا نُزِّلَ عَلَيْهِ ٱلْقُرْءَانُ جُمْلَةً وَٰحِدَةً ۚ كَذَٰلِكَ لِنُثَبِّتَ بِهِۦ فُؤَادَكَ ۖ وَرَتَّلْنَـٰهُ تَرْتِيلًا
Asad Quran Translation
Now they who are bent on denying the truth are wont to ask, "Why has not the Qur'an been bestowed on him from on high in one single re-velation?" 26
[It has been revealed] in this manner so that We might strengthen thy heart thereby-for We have so arranged its component parts that they from one consistent whole.27
Lit., "in one piece" or "as one statement" (jumlatan wahidatan) - implying, in the view of the opponents of Islam, that the gradual, step-by-step revelation of the Qur'an points to its having been "composed" by Muhammad to suit his changing personal and political requirements.
I.e., free of all inner contradictions (cf. 4:82 ). See also 39:23 , where the Qur'an is spoken of as "fully consistent within itself". The concise phrase rattalnahu tartilan comprises the parallel concepts of "putting the component parts [of a thing] together and arranging them well" as well as "endowing it with inner consistency". Inasmuch as full consistency and freedom from contradictions in a message spread over twenty-three years of a life as full of movement and drama as that of the Prophet does give a clear indication of its God-inspired quality, it is bound to strengthen the faith of every thinking believer: and herein lies, according to the Qur'an itself, the deepest reason for its slow, gradual revelation. (When applied to the reciting of the Qur'an - as in 73:4 - the term tartil refers to the measured diction and the thoughtful manner in which it ought to be enunciated.)
Malik Quran Translation
The unbelievers ask: "Why is not the Qur'an revealed to him all in a single revelation?" This method of slow, well arranged, piecemeal revelations is adopted to strengthen your heart.
Yusuf Ali Quran Translation
Those who reject Faith say: "Why is not the Qur'an revealed to him all at once?" Thus (is it revealed) that We may strengthen thy heart thereby and We have rehearsed it to thee in slow well-arranged stages gradually. 3088
Three reasons are given for the gradual revelation of the Qur-an. (1) "To strengthen thy heart": the tremendous task of winning the Arab nation, and, through them, the whole world, to Islam, required superhuman patience, constancy, and firmness, and these qualities were strengthened by the gradual promulgation of solutions to each difficulty as it arose. (2) "Slow, well-arranged stages": though the stages were gradual, as the occasion demanded from time to time, in the course of twenty-three years, the whole emerged, when completed, as a well-arranged scheme of spiritual instruction, as we have seen in following the arrangement of the Suras. (3) Questions put and answers given: see next note.
Mustafa Khattab Quran Translation
The disbelievers say, “If only the Quran had been sent down to him all at once!” ˹We have sent it˺ as such ˹in stages˺ so We may reassure your heart with it. And We have revealed it at a deliberate pace.
Piktal Quran Translation
And those who disbelieve say: Why is the Qur'an not revealed unto him all at once? (It is revealed) thus that We may strengthen thy heart therewith; and We have arranged it in right order.
Waqala allatheena kafaroo lawla nuzzila AAalayhi alquranu jumlatan wahidatan kathalika linuthabbita bihi fuadaka warattalnahu tarteelan