حَدَّثَنَا وَكِيعٌ عَنْ سُفْيَانَ عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ عَنِ ابْنِ عُمَرَ قَالَ بَيْنَا النَّاسُ فِي مَسْجِدِ قُبَاءَ فِي صَلَاةِ الصُّبْحِ إِذْ أَتَاهُمْ آتٍ فَقَالَ إِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَدْ نَزَلَ عَلَيْهِ قُرْآنٌ وَوُجِّهَ نَحْوَ الْكَعْبَةِ قَالَ فَانْحَرَفُوا
مسند امام احمد بن حنبل · Hadith 4794
It was narrated that Ibn 'Umar said: Whilst the people were in the mosque of Quba', praying Fajr, someone came to them and said: Qur'an was revealed to the Messenger of Allah (PBUH) last night, and he was commanded to turn towards the Ka'bah (in prayer). So they turned towards it.
Sanad
حَدَّثَنَا وَكِيعٌ عَنْ سُفْيَانَ عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ عَنِ ابْنِ عُمَرَ