Musannaf Ibn Abi Shayba 36:277

Waki’ ibn al-Jarrah narrated to us, he said: ‘Abd al-Wahid ibn Ayman narrated to us, from his father, from Jabir ibn ‘Abd Allah, who said: The Prophet, may Allah bless him and grant him peace, and his companions remained digging the trench for three days without tasting any food. They said: "O Messenger of Allah, there is a hard rock here in the mountain." The Messenger of Allah, may Allah bless him and grant him peace, said: "Sprinkle water upon it." So they sprinkled it. Then the Prophet, may Allah bless him and grant him peace, came and took the pickaxe or the shovel, then said: "In the name of Allah," and struck it three times, and it became like a sand dune. Jabir said: I happened to glance, and I saw the Messenger of Allah, may Allah bless him and grant him peace, had tied a stone against his stomach.