(a) It is narrated from Sayyiduna Rifa'ah bin Rafi' (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) — he related the story of the man's prayer. In it, what the Prophet (peace and blessings be upon him) taught that man is: "When you stand for prayer, perform ablution as Allah has commanded you. Then recite the tashahhud, then stand and say the takbir. If you know some of the Qur'an, recite it; otherwise, praise Allah, declare His greatness and say 'La ilaha illallah' (There is no god worthy of worship except Allah)."
(b) At the end of it, it says: "If you leave out anything from it, you will have reduced your prayer by that much."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3975