Sayyiduna Talq bin Ali (may Allah be pleased with him) said: I came to the Messenger of Allah (peace and blessings be upon him) while he (peace and blessings be upon him) was laying the foundations of the Prophet's Mosque, so I too began carrying stones as the others were carrying them. The Prophet (peace and blessings be upon him) said: "You, the people of Yamamah, are the most skilled at mixing clay, so mix the clay for us." So I would mix the clay for them, and they would carry it.
Hadith Referenceالمعجم الكبير للطبراني / باب الطاء / 8208