Al-Muzzammil • BN-TAFSEER-IBN-E-KASEER
﴿ وَٱذْكُرِ ٱسْمَ رَبِّكَ وَتَبَتَّلْ إِلَيْهِ تَبْتِيلًۭا ﴾
“But [whether by night or by day,] remember thy Sustainer's name, and devote thyself unto Him with utter devotion.”
Please check ayah 73:9 for complete tafsir.