"Arise [to pray] the night, except for a little - half of it, or subtract from it a little, or add to it."
Muhammad said: (Half of it); meaning: stand for half of it.
"And recite the Quran with measured recitation," meaning: recite it slowly and distinctly.
﴿قُم اللَّيْل إلاقليلاً نِصْفَهُ أَوِ انْقُصْ مِنْهُ قَلِيلا أَو زد عَلَيْهِ﴾.
قَالَ محمدٌ: (نِصْفَهُ)؛ أَيْ: قُمْ نصفه.
﴿ورتل الْقُرْآن ترتيلا﴾ أَي: ترسَّل فِيهِ ترسُّلا