Rukoo is a pillar of the prayer.
Learn about it with these resources.
The Messenger –sallAllaahu alayhi wa sallam- used to order to being tranquil in the Rukoo’; and he said to the person who did not pray properly:
‘then raise your head until you are standing straight; [until every bone goes back to its place], (and in a narration: ‘and when rise from Rukoo’; then straighten your back, and raise your head until the bones go back to their joints’)
And the Messenger –sallAllaahu alayhi wa sallam- mentioned: ‘that no one’s prayer is complete, if he does not do that.’(Source)
Learn About Rukoo
Prophet's (ﷺ) prayer described - Correcting the Imaam & The Rukoo | Seif Abū InaayahThe section on Rukoo starts at around 3:15 of the audio.
The Bowing (Rukoo)
From: The Abridgement Of The Prophet’s Prayer Described – Shaykh Al-Albaani (via AbdurRahman.org)
THE BOWING (RUKOO’)
(69) When he has finished reciting he remains silent for a moment, long enough to return his breathing to normal.
(70) Then he raises his hands, in the manner described previously with regard to the initial takbeer (point nos. 33, 34 and 35).
(71) He also says the takbeer (i.e., Allaahu Akbar), and this is obligatory.
(72) Then he performs the rukoo’ (i.e., bows) in such a manner that all his joints are settled, and each part of the body is at rest. This is a pillar (rukn).
HOW THE BOWING (RUKOO’) IS PERFORMED
(73) He should place his hands firmly upon his knees. He should spread his fingers, as if he were grasping his knees. All of this is obligatory.
(74) He should stretch out his back and make it level, such that if water were to be poured upon it, then it would settle upon it. This is an obligation.
(75) He should neither cause his head to droop lower than his back, nor should he raise it above it. Rather he should make it level with his back.
(76) He should keep his elbows (straight and) apart from his sides.
(77) He should say in his rukoo’:
Subhaana Rabbee al-‘Azeem
I declare my Lord, the Supreme, free and far removed from all imperfections. [15]
Saying it three times, or more.
(78) From the Sunnah is that he makes the pillars of equal length. So he should make his rukoo’, his sujood (prostration), and his sitting between the two prostrations of similar length.
(79) It is not allowed for him to recite the Qur’aan in the rukoo’ (bowing), nor in the sujood (prostration).
STRAIGHTENING UP FROM THE RUKOO’
(80) Then he must raise up and straighten his back from the rukoo’. This is a pillar.
(81) He must say, while raising his back:
Sami’ Allaahu liman hamidah
Allaah listens and responds to the one who praises Him. This is an obligation.
(82) He should raise his hands when he rises up, in the manner that has preceded (point nos. 33, 34 and 35).
(83) Then he should stand straight up and remain still, such that every bone returns to its place. This is a pillar.
(84) He should say while standing:
Rabbanaa wa lakal-hamd
O our Lord! And all praise is for You.[16]
This is obligatory upon everyone praying, even if he is praying behind an imaam [17], since it is the saying prescribed for this standing position. As for the saying, then it is the saying prescribed to be said whilst rising.
(85) He should make this standing about as long as the rukoo’ (bowing), as has preceded.
Audio of the dhikr for rukoo can be found here.
The Place of Looking in Rukoo
Shaikh al-Albaani:
“He is not obliged to look at a certain spot like he should when he is standing and when he is sitting for the tashahhud. So when he is standing, he looks at the place of his prostration; and when he is sitting during the tashahhud, he looks at his (right index) finger. But during rukoo`, there isn’t a specific spot toward which we were commanded to look, so the matter is unrestricted.”
How Many Takbeers Does One Make When Joining the Congregational Prayer & the Imaam is in Rukoo’ or Other Than it?
The Sunnah in Observing The Rukoo’ And The Subsequent Sujood Behind The Imaam – By Shaikh Al-Albaanee (discusses the followers waiting for the imam's face to touch the ground in sujood before they go down into sujood.
Learning Aids
Rukoo Lesson (based upon Prophet's Prayer Described)Sujood (and Rukoo) Concept Flash cards
Review/learn the dhikr of sujood and other concepts related to it. (Word DOC, formatted for printing on 3x5 cards only; answers are not provided, students can write them on the back) (I embedded the fonts into the document but if they don't show up for you, the big, thick bold font is KG Second Chances. Just install it on your computer and it should show up when you open the document).
Students write the answers under the flaps