Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "Indeed, the worst thief is the one who steals his prayer." The people submitted, "O Messenger of Allah, how does he steal it?" The Prophet (peace and blessings be upon him) said: "He does not complete its ruku' (bowing) and its sujud (prostrations)."
Imam Ahmad, Imam al-Bazzar and Imam Abu Ya'la recorded this narration. Its chain contains a narrator, Ali bin Zayd, and there is disagreement about using him as evidence; the remaining narrators of this narration are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2720