Hadith
أَخْبَرَنَا هَنَّادُ بْنُ السَّرِيِّ، فِي حَدِيثِهِ عَنْ أَبِي الأَحْوَصِ، عَنْ حُصَيْنٍ، عَنْ كَثِيرٍ، - وَهُوَ ابْنُ مُدْرِكٍ - عَنْ عَبْدِ الرَّحْمَنِ بْنِ يَزِيدَ، قَالَ قَالَ ابْنُ مَسْعُودٍ وَنَحْنُ بِجَمْعٍ سَمِعْتُ الَّذِي، أُنْزِلَتْ عَلَيْهِ سُورَةُ الْبَقَرَةِ يَقُولُ فِي هَذَا الْمَكَانِ " لَبَّيْكَ اللَّهُمَّ لَبَّيْكَ " .
It was narrated that Abdur-Rahman bin Yazid said:"When we were in Jam (Al-Muzadalifah), Ibn Masud said: 'I heard the one to whoem surat Al-Baqarah was revealed say, in this place: Labbaik Allahumma Labbaik
Sahih · Abu Ghuddah
Sunan an-Nasa'i 3046 ·Book 24, Hadith 429·Also available on sunnah.com·