73:6
إِنَّ نَاشِئَةَ ٱلَّيْلِ هِىَ أَشَدُّ وَطْـًٔا وَأَقْوَمُ قِيلًا
inna nāshi-ata al-layli hiya ashaddu waṭan wa-aqwamu qīlan
Night prayer makes a deeper impression and sharpens words––
Verily, the rising by night (for Tahajjud prayer) is very hard and most potent and good for governing oneself, and most suitable for (understanding) the Word (of Allâh).