Sahih Bukhari Volume 1, Book 8, Hadith 403

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، قَالَ أَخْبَرَنَا مَالِكُ بْنُ أَنَسٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، قَالَ بَيْنَا النَّاسُ بِقُبَاءٍ فِي صَلاَةِ الصُّبْحِ إِذْ جَاءَهُمْ آتٍ فَقَالَ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَدْ أُنْزِلَ عَلَيْهِ اللَّيْلَةَ قُرْآنٌ، وَقَدْ أُمِرَ أَنْ يَسْتَقْبِلَ الْكَعْبَةَ فَاسْتَقْبِلُوهَا، وَكَانَتْ وُجُوهُهُمْ إِلَى الشَّأْمِ، فَاسْتَدَارُوا إِلَى الْكَعْبَةِ‏

Narrated By 'Abdullah bin 'Umar : While the people were offering the Fajr prayer at Quba (near Medina), someone came to them and said: "It has been revealed to Allah's Apostle tonight, and he has been ordered to pray facing the Ka'ba." So turn your faces to the Ka'ba. Those people were facing Sham (Jerusalem) so they turned their faces towards Ka'ba (at Mecca).