Does prayer become deficient due to not completing the bowing (rukūʿ) or prostration (sujūd), or the sitting between the two prostrations, due to a physical ailment or ignorance?

Summary: The aforementioned hadith has been reported as both marfu' (attributed to the Prophet) and mawquf (attributed to a Companion). The majority of scholars prefer its mawquf attribution to Abu Hurairah, may Allah be pleased with him. Some scholars have graded its marfu' chain of transmission as hasan (good) due to supporting narrations from the Companions' statements, such as the hadith of Hudhayfah, may Allah be pleased with him.

The meaning of the hadith is that a person who does not complete the pillars of prayer, such as bowing, prostrating, and having ṭuma'nīnah (tranquility), will not have their prayer accepted. This applies to anyone who is negligent, careless, or lazy in performing the prayer correctly, falling into this due to ignorance resulting from their own negligence. As for someone who exerts their effort, learns what is required of them, and then errs or is unable to complete it due to an acceptable excuse, they are not blamed, and they are hoped to receive reward for their intention. For Allah does not burden a soul beyond its capacity. One should also avoid waswasah (obsessive whispering) and despair in worship.