Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) said: "Before the mosque was built, the Messenger of Allah (peace and blessings be upon him) used to pray facing a piece of wood. Then, when the mosque was built, a mihrab was made for him. He (peace and blessings be upon him) stepped forward towards it, and the piece of wood wailed like a camel. Then the Messenger of Allah (peace and blessings be upon him) placed his hand on it, and it became still."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5705