It is narrated from Hazrat Abu Masood that the Messenger of Allah, peace and blessings be upon him, said: The prayer of that person is not correct whose back is not straight in bowing (ruku) and prostration (sajdah).

Hazrat Ali (may Allah be pleased with him) bin Shiban says that we came to the service of the Prophet (peace and blessings be upon him) as a delegation, and we pledged allegiance at his hand and prayed with him. During the prayer, the Prophet (peace and blessings be upon him) glanced at a man whose back was not straight in bowing and prostration. When the Prophet (peace and blessings be upon him) completed the prayer, he said: O group of Muslims! The prayer of that person is not valid whose back is not straight in bowing and prostration.

Hazrat Ali (may Allah be pleased with him) bin Yahya bin Khallad narrates from his father, and he from his uncle, that once we were sitting with the Messenger of Allah (peace and blessings be upon him) when a man came and performed the prayer very quickly, not performing the bowing (ruku) and prostration (sujud) properly. The Noble Prophet (peace and blessings be upon him) was staring at him, while we did not realize this. When he finished his prayer and came to the presence of the Prophet (peace and blessings be upon him) and greeted him, the Prophet (peace and blessings be upon him) replied to his greeting and said, "Repeat the prayer, you have not prayed." He did this three times, but each time the Prophet (peace and blessings be upon him) told him, "Repeat the prayer, you have not prayed." When he came the fourth time, he said, "O Messenger of Allah! Teach me the prayer, by Allah! I have tried my best." The Prophet (peace and blessings be upon him) said, "When you stand for prayer, face the Qiblah. Then say the takbir, then recite (Qur'an), then bow and perform the bowing with calmness. Then when you rise from bowing, stand with calmness. Then prostrate and perform the prostration with calmness. Then when you sit, sit with calmness, and then stand up again. If you do this, your prayer is complete, and if you fall short in any of these actions, know that there is a deficiency in your prayer."

Hazrat Abu Huraira narrates that a man entered the mosque and offered prayer. The Holy Prophet (peace and blessings be upon him) was sitting in a corner of the mosque. The man came and greeted the Holy Prophet (peace and blessings be upon him). The Prophet replied to his greeting and said, "Go and pray, for you have not yet prayed." The man went and after returning, greeted again, so the Messenger of Allah (peace and blessings be upon him) said, "Go, you have not yet prayed." Then for the third time, the man said, "O Messenger of Allah! Teach me how to pray." The Prophet (peace and blessings be upon him) said, "When you stand for prayer, perform ablution properly, then face the Qiblah and say the Takbeer. Then recite from the Holy Qur'an whatever is easy for you. Then bow with calmness, then stand up straight with full composure, then prostrate with calmness, then stand up straight or he said, then sit straight. Then perform these actions throughout your prayer."

It is narrated from Hazrat Abu Saeed Khudri that the Messenger of Allah, peace and blessings be upon him, said: "The worst thief is the one who steals in prayer." The people asked, "O Messenger of Allah! How can one steal in prayer?" He replied, "By not performing its bowing and prostration properly."

Hazrat Thabit narrates that once Hazrat Anas described to us the way the Messenger of Allah (peace and blessings be upon him) performed prayer. First, he stood straight for prayer, then he bowed (in ruku‘), then he raised his head from ruku‘, then stood up straight. And he remained standing for so long that some of us thought he had forgotten. Then Hazrat Anas performed sajdah, then sat up straight, and remained sitting for so long that some of us thought he had forgotten.

Hazrat Salim Barad says that we went to the house of Hazrat Abu Masood and requested him to teach us the prayer of the Messenger of Allah, peace and blessings be upon him. He stood before us for prayer, then he bowed (in ruku) and placed his palms on his knees and his fingers below his knees. He kept his elbows away from his body in such a way that every part of the body became straight. Then he raised his head and said "Sami Allahu liman Hamidah." Then he stood in such a way that every part of the body was in balance, then he performed prostration (sajdah) and did the same in prostration. Then he performed two units (rak'ahs) of prayer. When he finished, he said that we saw the Messenger of Allah, peace and blessings be upon him, praying in this manner.

Hazrat Abu Hurairah says that a man keeps offering prayers for sixty years, but his prayer is not accepted, because sometimes he performs the bowing (ruku) properly but not the prostration (sajdah), and sometimes he performs the prostration properly but not the bowing.

Hazrat Muhammad bin Amr says that I saw Hazrat Abu Humaid Sa'idi with ten companions. Hazrat Abu Humaid said, "Shall I not describe to you the way the Messenger of Allah (peace and blessings be upon him) performed prayer?" They said, "Certainly, do so." He said, "When the Messenger of Allah (peace and blessings be upon him) would raise his head from bowing (ruku'), he would remain still for so long that every bone would return to its place, then he would bend to go into prostration (sajdah) and then say the takbeer."

Hazrat Aisha (may Allah be pleased with her) narrates that when the Messenger of Allah (peace and blessings be upon him) performed ruku, he would not lower his blessed head below his back nor raise it above, but would keep it in a position between the two. When he raised his head from ruku, he would not go into prostration until he stood up straight in an upright position. And when he raised his head after prostration, he would not perform the second prostration until he sat in a state of calmness. After every two rak‘ahs, he used to recite at-Tahiyyat.