Musnad Ahmad 32:1235

Rawh narrated to us, Hammad narrated to us, from Thabit, from Anas ibn Malik, from the Prophet, peace and blessings of Allah be upon him, regarding the saying of the Almighty, the Majestic: {And when his Lord manifested Himself to the mountain} [Al-A'raf: 143]. He said: "He gestured with his little finger." He said: "So it crumbled."