Musannaf Ibn Abi Shayba 36:286

Hawdha ibn Khalifa narrated to us, he said: Awf narrated to us, from Maymun, he said: Al-Bara’ ibn Azib narrated to us, he said: When it was the time that the Messenger of Allah, may Allah bless him and grant him peace, commanded us to dig the trench, a great, hard rock appeared to us in a part of the mountain, which the pickaxes could not penetrate. We complained about that to the Messenger of Allah, may Allah bless him and grant him peace. The Messenger of Allah, may Allah bless him and grant him peace, came, and when he saw it, he took the pickaxe, cast aside his garment, and said: "In the name of Allah," then he struck a blow and broke a third of it. He said: "Allah is the Greatest! I have been given the keys of Ash-Sham. By Allah, I am looking at its red palaces right now." Then he struck a second blow and cut another third. He said: "Allah is the Greatest! I have been given the keys of Persia. By Allah, I am looking at the white palace of Al-Mada'in." Then he struck a third blow and said: "In the name of Allah," and he cut the remainder of the rock. He said: "Allah is the Greatest! I have been given the keys of Yemen. By Allah, I am looking at the gates of Sana'a."