Sayyiduna al-Bara' bin Azib (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) ordered us to dig the trench. At one place in the trench a rock confronted us on which the pickaxes had no effect. The people complained about it to the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) came. The narrator says: I think the words in the narration are: He put down his garment and climbed onto the rock. He took hold of the pickaxe and said: "In the name of Allah." Then he struck one blow, and a third of the stone (i.e. the rock) broke off. The Prophet (peace and blessings be upon him) said: "Allah is the Greatest! I have been given the keys of Syria. By Allah! From this place of mine I can see its red palaces." Then he said: "In the name of Allah," and struck a second blow, and another third of it broke off. The Prophet (peace and blessings be upon him) said: "Allah is the Greatest! I have been given the keys of Persia, and I can see the cities (or the city called al-Mada'in), and from this place of mine I can see its white palace." Then the Prophet (peace and blessings be upon him) said: "In the name of Allah," and he struck another blow and broke the rest of the stone as well. He said: "Allah is the Greatest! I have been given the keys of Yemen, and standing in this place of mine I can see the gates of San'a'."
Ahmad recorded it; its chain contains Maymun Abu Abdullah, whom Ibn Hibban declared thiqah (trustworthy) while a group declared him da'if (weak); the rest of its narrators are thiqat (trustworthy).