Sunan Ibn Majah, Book 5, Hadith 882 (In-Book) ⓘ
It was narrated that Ibn ‘Umar said: “The Prophet used to recite in the Maghrib: ‘Say: O you disbelievers!’[Al-Kafirun (109)] and ‘Say: He is Allah, (the) One.’”[Al-Ikhlas (112)]
حَدَّثَنَا أَحْمَدُ بْنُ بُدَيْلٍ، حَدَّثَنَا حَفْصُ بْنُ غِيَاثٍ، حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ كَانَ النَّبِيُّ ـ صلى الله عليه وسلم ـ يَقْرَأُ فِي الْمَغْرِبِ {قُلْ يَا أَيُّهَا الْكَافِرُونَ} وَ {قُلْ هُوَ اللَّهُ أَحَدٌ} .
also referenced under: Hadith 833 (Reference) & Volume 2, Book 5, Hadith 833 (DarusSalam)