Al-Muzzammil 73:6
إِنَّ نَاشِئَةَ ٱلَّيْلِ هِىَ أَشَدُّ وَطْـًٔا وَأَقْوَمُ قِيلًا
Inna nashi-ata allayli hiya ashaddu wat-anwaaqwamu qeela
"Indeed, the hours of the night are more effective for concurrence [of heart and tongue] and more suitable for words."
Al-Muzzammil 73:6, translation by Sahih International
A short reflection
Indeed, the hours of the night are more effective for concurrence of heart and tongue, and more clear in speech.