Hadith on Quran: Surat al-Ikhlas is one-third, al-Kafirun is one-forth

Abdullah ibn Umar reported: The Messenger of Allah, peace and blessings be upon him, said, “The chapter, ‘Say: He is Allah the One,’ (112:1) is equal to one-third of the Quran. The chapter, ‘Say: O unbelievers,’ (109:1) is equal to one-fourth of the Quran.” Ibn Umar said, “The Prophet would recite either of them in his two cycles before dawn prayer.”

Source: al-Mu’jam al-Kabīr 13319

Grade: Sahih li ghayrihi (authentic due to external evidence) according to Al-Albani

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 قَالَ ابْن عُمَرَ وَكَانَ يَقْرَأُ بِهِمَا فِي رَكْعَتَيِ الْفَجْرِ

13319 المعجم الكبير للطبراني

583 المحدث الألباني خلاصة حكم المحدث صحيح لغيره في صحيح الترغيب