Sayyiduna Abu Qatadah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "The worst of people in stealing is the one who steals from his prayer." The Companions (may Allah be pleased with them) asked: O Messenger of Allah, how does one steal from the prayer? He (peace and blessings be upon him) said: "By not completing its bowing and its prostrations."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3996
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
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
Harmalah, the freed slave of Sayyiduna Usamah bin Zayd (may Allah be pleased with him), narrates that once he was sitting with Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) when al-Hajjaj bin Ayman, the son of Umm Ayman, came in. He was a man of the Ansar, and Ayman was the elder brother of Sayyiduna Usamah bin Zayd (may Allah be pleased with him). Harmalah says: Al-Hajjaj offered a prayer in which he did not complete his bowing and prostrations. When he said the salam, Sayyiduna Ibn Umar (may Allah be pleased with them both) called him and said: "O my nephew, do you think that you have prayed? Your prayer has not counted; repeat your prayer." When al-Hajjaj had gone, Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said to me: "Who was this?" I said: Al-Hajjaj bin Ayman, the son of Umm Ayman. Sayyiduna Ibn Umar (may Allah be pleased with them both) said: "Had the Messenger of Allah (peace and blessings be upon him) seen him, he would have loved him." Then he mentioned the reason for that love: that he was among the offspring of Umm Ayman (may Allah be pleased with her), and Umm Ayman (may Allah be pleased with her) was the one who nursed and cared for the Prophet (peace and blessings be upon him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3999