Musnad Ahmad 30:2620

Waki’ narrated to us, he said: Sufyan narrated to us, from Suhayl ibn Abi Salih, from ‘Abdullah ibn Dinar, from Abi Salih, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Faith consists of seventy-odd branches. The lowest of them is removing harm from the road, and the highest of them is the saying: 'There is no god but Allah.'"