Sunan an-Nasa'i, Hadith 989 ⓘ
It was narrated from Zaid bin Thabit that : He said to Marwan: "O Abu Abdul-Malik, do you recite: 'Say: He is Allah, (the) One' and 'Verily, We have granted you Al-Kawthar' in maghrib?" He said: "Yes." He (Zaid) said: "I swear by Allah, I saw the Messenger of Allah reciting the longer of the two long surahs in it: 'Alif-Lam-Mim-Sad.'"
أَخْبَرَنَا مُحَمَّدُ بْنُ سَلَمَةَ، قَالَ حَدَّثَنَا ابْنُ وَهْبٍ، عَنْ عَمْرِو بْنِ الْحَارِثِ، عَنْ أَبِي الأَسْوَدِ، أَنَّهُ سَمِعَ عُرْوَةَ بْنَ الزُّبَيْرِ، يُحَدِّثُ عَنْ زَيْدِ بْنِ ثَابِتٍ، أَنَّهُ قَالَ لِمَرْوَانَ يَا أَبَا عَبْدِ الْمَلِكِ أَتَقْرَأُ فِي الْمَغْرِبِ بِـ { قُلْ هُوَ اللَّهُ أَحَدٌ } وَ { إِنَّا أَعْطَيْنَاكَ الْكَوْثَرَ } قَالَ نَعَمْ . قَالَ فَمَحْلُوفَةٌ لَقَدْ رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقْرَأُ فِيهَا بِأَطْوَلِ الطُّولَيَيْنِ { المص } .
also referenced under: Book 11, Hadith 114 (In-Book) & Volume 2, Book 11, Hadith 990 (DarusSalam)