We were digging (the trench) on the day of [Al-Khandaq (i.e. the Trench)] and we came across a big solid rock. We went to the Prophet (ﷺ) and said, "Here is a rock appearing across the trench." He said, I am coming down." Then he got up, and a stone was tied to belly for we had not eaten anything for three days. So the Prophet (ﷺ) took the spade and struck the big solid rock and it became like sand. [5:427-O.B]