Calmness in bowing

It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) was in the mosque; then he related in detail the story of the man who did not perform the prayer well, until the Messenger of Allah (peace and blessings be upon him) taught him the prayer. In what the Messenger of Allah (peace and blessings be upon him) taught him there is also: "Then bow until you are at ease in bowing."

It is narrated from Sayyiduna Abu Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The prayer of a man who does not straighten his back in bowing and prostration is not complete."

It is narrated from Sayyiduna Abu Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The prayer of a man who does not level his back in bowing and prostrations is insufficient."
This chain is sahih (authentic).

It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "A prayer in whose bowing and prostration a man does not level his back is of no avail."
Only Yahya bin Abi Bukayr narrated it.

It is narrated from Abu Abdullah al-Ash'ari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) led his Companions in prayer, then sat with a group of them. Meanwhile a man entered the mosque and began to pray, but he was not performing the bowing properly and was pecking in his prostrations, while the Messenger of Allah (peace and blessings be upon him) was watching him. He (peace and blessings be upon him) said: "Do you see this man? If he dies in this state, he will die upon a religion other than the religion of Muhammad (peace and blessings be upon him). He pecks in his prayer as a crow pecks at blood. The likeness of one who prays in such a way that he does not perform the bowing properly and pecks (like a crow) in his prostrations is that of a hungry man who can eat only one or two dates; how will they suffice him? So perform ablution thoroughly. Woe and the threat of the Fire are for those with (dry) heels! And complete the bowing and prostration."
Abu Salih said: I asked Abu Abdullah al-Ash'ari (may Allah be pleased with him): Who narrated this hadith to you? He said: The commanders of the armies, namely Khalid bin al-Walid, Amr bin al-As, Shurahbil bin Hasanah and Yazid bin Abi Sufyan (may Allah be pleased with them), narrated it, and all of them heard this hadith from the Messenger of Allah (peace and blessings be upon him).