While some people were offering Fajr prayer at Quba' (mosque), some-one came to them and said, "Tonight some Qur'anic Verses have been revealed to the Prophet (ﷺ) and he has been ordered to face the Ka`ba (at Mecca) (during prayers), so you too should turn your faces towards it." At that time their faces were towards Sham (Jerusalem) so they turned towards the Ka`ba (at Mecca).