Musnad Ahmad 1017:29

Isma'il narrated to us, 'Uyaynah ibn 'Abd al-Rahman narrated to us, from his father, from Buraydah al-Aslami, who said: I went out one day for a need, and suddenly I was with the Prophet, peace and blessings of Allah be upon him, walking before me. He took my hand, and we set off walking together. Suddenly, we were before a man praying, who was performing many bowings and prostrations. The Prophet, peace and blessings of Allah be upon him, said: "Do you see him showing off?" I said: "Allah and His Messenger know best." He let go of my hand from his hand, then he brought his hands together and began to lower and raise them, saying: "Upon you is a moderate path. Upon you is a moderate path. Upon you is a moderate path; for whoever overburdens this religion, it will overcome him."