Musnad Ahmad 32:1029

Isma'il narrated to us, Sulayman al-Taymi informed us, Anas ibn Malik narrated to us, he said: It was mentioned to me that the Prophet 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—meaning—they amaze the people, and they are amazed by themselves. They pass through the religion just as the arrow passes through the target."