Musnad Ahmad 32:943

Yahya narrated to us, from al-Taymi, from Anas, who said: It was mentioned to me that the Messenger of Allah (peace and blessings of Allah be upon him) said—and I did not hear it from him—: "Indeed, among you are people who worship and toil until people are amazed by them, and they are amazed by themselves. They pass through the religion just as an arrow passes through the game."