Musnad Ahmad 27:195

Yahya ibn Sa'id narrated to us, from Sufyan, Abdullah ibn Dinar narrated to me, I heard Ibn Umar saying: While the people were praying the morning prayer in the Mosque of Quba, a comer came and said: "Indeed, a Quran has been revealed to the Messenger of Allah (ﷺ) tonight, and he has been commanded to face the Kaaba, so face it." They turned around and directed themselves toward the Kaaba.