Zayd b. Wahb reports:
We were once sitting in the masjid with Hudhayfah (ibn Al-Yamân) – Allah be pleased with him, when a man entered from the gates of Kindah and stood to pray; but he did not complete the bowing or prostration postures. When he had finished praying, Hudhayfah asked him, “How long have you been praying in this manner?” The man replied, “For forty years.” Hudhayfah said, “You have not prayed for forty years! And if you were to die praying in this manner you would die upon a way (fitrah) other than the way of Muhammad – Allah’s peace and blessings be upon him.”
Al-Bukhârî, Al-Sahîh, The Book of Adhân, without the mention of 40 years. A version in Al-Nasâ`î, Chapter on the Deficient Prayer, mentions the question and reply about 40 years. Shaykh Al-Albânî graded its chain of transmission sahîh in Sahîh Sunan Al-Nasâ`î no. 1311.