Abdullah ibn Umar reported: The Messenger of Allah, peace and blessings be upon him, said, “Say: He is Allah the One (112:1) is equal to one third of the Quran. Say: O unbelievers (109:1) is equal to one fourth of the Quran.” The Prophet would recite these two in his bowings before the dawn prayer.
Source: Mu’jam Al-Kabeer 13319
Grade: Hasan (fair) according to Al-Mundhiri
عَنِ ابْنِ عُمَرَ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قُلْ هُوَ اللَّهُ أَحَدٌ تَعْدِلُ ثُلُثَ الْقُرْآنِ وَ قُلْ يَأَيُّهَا الْكَافِرُونَ تَعْدِلُ رُبْعَ الْقُرْآنِ وَكَانَ يَقْرَأُ بِهِمَا فِي رَكْعَتَيِ الْفَجْرِ
13319 المعجم الكبير للطبراني باب التاء باب
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