﴿ أَوْ زِدْ عَلَيْهِ وَرَتِّلِ ٱلْقُرْءَانَ تَرْتِيلًا ﴾

“or add to it [at will]; and [during that time] recite the Qur’an calmly and distinctly, with thy mind attuned to its meaning.”

(Or add (a little) thereto) or pray more than half of the night, up to two thirds of the night, thus giving him a choice, and then He said: (and chant the Qur'an in measure) recite the Qur'an deliberately, unhurriedly and with gravity, i.e. reciting two or three verses each time until you finish the whole recitation,