It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "In terms of stealing, the worst of people is the one who steals from his prayer." The Companions (may Allah be pleased with them) asked: O Messenger of Allah (peace and blessings be upon him), how does a person steal from the prayer? He (peace and blessings be upon him) said: "He does not complete its bowing and its prostrations."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3997