Zayd bin Wahb narrates: Sayyiduna Hudhayfah (may Allah be pleased with him) saw a man who was not performing the bowing and the prostrations completely, and said to him: For how long have you been praying (like this)? He replied: For forty years. Sayyiduna Hudhayfah (may Allah be pleased with him) said: You have not prayed at all, and if you die in this state, you will not die upon the fitrah (Islam).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3998