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 Messenger (ﷺ) 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).
Reference: Sahih al-Bukhari 403 In-book : Book 8, Hadith 55 USC-MSA web (English) : Vol. 1, Book 8, Hadith 397 (deprecated)
Help us gift a modern, ad-free Islamic application for the Muslim Ummah. Your donation will be recorded as Sadaqah Jariyah in your book of deeds, In Sha Allah.