Al-Muzzammil • BN-TAFSEER-IBN-E-KASEER
﴿ أَوْ زِدْ عَلَيْهِ وَرَتِّلِ ٱلْقُرْءَانَ تَرْتِيلًا ﴾
“or add to it [at will]; and [during that time] recite the Qur’an calmly and distinctly, with thy mind attuned to its meaning.”
Please check ayah 73:9 for complete tafsir.