The Book of Pilgrimage
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو الأَحْوَصِ، عَنْ حُصَيْنٍ، عَنْ كَثِيرِ بْنِ مُدْرِكٍ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ يَزِيدَ، قَالَ قَالَ عَبْدُ اللَّهِ وَنَحْنُ بِجَمْعٍ سَمِعْتُ الَّذِي أُنْزِلَتْ عَلَيْهِ سُورَةُ الْبَقَرَةِ يَقُولُ فِي هَذَا الْمَقَامِ " لَبَّيْكَ اللَّهُمَّ لَبَّيْكَ " .Abdullah narrated to us as we had gathered (at Muzdalifa):I have heard from one upon whom Surah al-Baqara was revealed (the Holy Prophet) pronouncing Talbiya at this place
From Sahih Muslim, whose reports the scholars accept as authentic.