The Prophet (ﷺ) ﷺ asked:

“Is any one of you unable to recite one-third of the Qur'ān in one night? They said: How could anyone read one-third of the Qur'ān (in one night)? He said: Qul huwa Allāhu aḥad (Sūrat al-Ikhlāṣ) is equivalent to one-third of the Qur'ān.” Reference: Sahih Muslim 811a.

عَنْ أَبِي الدَّرْدَاءِ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏"‏ أَيَعْجِزُ أَحَدُكُمْ أَنْ يَقْرَأَ فِي لَيْلَةٍ ثُلُثَ الْقُرْآنِ ‏" قَالُوا : وَكَيْفَ يَقْرَأْ ثُلُثَ الْقُرْآنِ؟ قَالَ : " قُلْ هُوَ اللَّهُ أَحَدٌ تَعْدِلُ ثُلُثَ الْقُرْآنِ " ‏.‏