Sahih Bukhari
Prophetic Commentary on the Quran (Tafseer of the Prophet (PBUH))
Volume: 006 / Book Number: 060 / Hadith Number: 17
Narrated Ibn 'Umar:
While some people were offering morning prayer at Quba' a man came to them and said, "A Quranic Order has been revealed to Allah's Apostle tonight that he should face the Ka'ba at Mecca (in prayer), so you too should turn your faces towards it." At that moment their faces were towards Sham (i.e. Jerusalem) (and on hearing that) they turned towards the Ka'ba (at Mecca).