voluntary worship

وَمِنَ ٱلَّيْلِ فَتَهَجَّدْ بِهِۦ نَافِلَةً لَّكَ عَسَىٰٓ أَن يَبْعَثَكَ رَبُّكَ مَقَامًا مَّحْمُودًا

And from [part of] the night, pray with it [i.e., recitation of the Qur’ān] as additional [worship] for you; it is expected that your Lord will resurrect you to a praised station.