Correct Postures in Sujud:

• He (sallallaahu 'alaihi wa sallam) used to say, There is no one among my ummah whom I will not recognise on the Day of Resurrection. They said, "How will you recognise them, O Messenger of Allaah, among the multitude of created beings?" He said, Do you not see that were one of you to enter an enclosure in which there was a jet black130 steed and a horse with a white forehead and legs131, would you not recognise the latter from the former? They said, "Of course." He said, Thus, my ummah on that day will surely have white faces132 because of sujood, and white arms and feet133 because of ablution.134 
• He would also say, When Allaah intends to have mercy on whomsoever he wishes of the people of the Fire, He will order the angels to bring out whoever used to worship Allaah; so they will bring them out, recognising them from the marks of sujood, for Allaah has prohibited the Fire from devouring the marks of sujood. Thus, they will be brought out from the Fire, for the Fire devours all of a son of Aadam except the marks of sujood.135

• He (sallallaahu 'alaihi wa sallam) used to command the completion of rukoo' and sujood, comparing someone not doing so to the hungry man who eats one or two dates, which are of no use to him, and also saying about him, he is indeed one of the worst thieves among the people. 
• He also ruled that the prayer of one who does not straighten his spine fully in rukoo' and sujood is invalid, as has been mentioned under "Rukoo'", and ordered "the one who prayed badly" to be at ease in his sujood, as mentioned before.

He (sallallaahu 'alaihi wa sallam) would say any one of the following remembrances of Allaah and supplications in this posture:

1. How Perfect is my Lord, the Most High, three times.114 Sometimes, "he would repeat it more times than that."115 Once, he repeated it so much that his sujood were nearly as long as his standing, in which he had recited three of the Long Soorahs: al-Baqarah, an-Nisaa' and aal-'Imraan. That prayer was full of supplication and seeking of forgiveness, as mentioned before under "Night Prayer". 
2. How Perfect is my Lord, the Most High, and Praised be He, three times.116 
3. Perfect, Blessed, Lord of the Angels and the Spirit.117 
4. How perfect You are O Allaah, our Lord, and Praised. O Allaah! Forgive me, which he would say often in his rukoo' and sujood, implementing the order of the Qur'aan.118 
5. O Allaah! For you I have prostrated; in You I have believed; to You I have submitted; [You are my Lord;] my face has prostrated for the One Who created it and shaped it , [shaped it excellently,] then brought forth its hearing and vision: [so] blessed be Allaah, the Best to Create!119 
6. O Allaah! Forgive me all my sins: the minor and the major, the first and the last, the open and the hidden.120 
7. My person and my shadow have prostrated to You; my heart has believed in You; I acknowledge Your favours towards me: here are my hands and whatever I have earned against myself.121 
8. How Perfect is He Who has all Power, Kingdom, Magnificence and Supremity122, which he would say in night prayer, as with the following ones: 
9. How perfect You are [O Allaah] and Praised. None has the right to be worshipped except you.123 
10. O Allaah! Forgive me what (sins) I have concealed and what (sins) I have done openly.124 
11. O Allaah! Place light in my heart; [and light in my tongue;] and place light in my hearing; and place light in my seeing; and place light from below me; and place light from above me, and light on my right, and light on my left; and place light ahead of me; and place light behind me; [and place light in my self;] and make the light greater for me.125 
12. [O Allaah!] [Indeed] I seek refuge with Your Pleasure from Your Anger; [I seek refuge] with Your Pardons from Your Punishment; I seek refuge with You from You. I cannot count all exultations upon You; You are as You have extolled Yourself.126

He (sallallaahu 'alaihi wa sallam) used to forbid recitation of the Qur'aan in rukoo' and sujood, and commanded striving in, and a lot of, supplication in this posture, as explained previously under "Rukoo'". He also used to say, The slave is closest to his Lord when he is prostrating, so increase supplication [in it].127  

He (sallallaahu 'alaihi wa sallam) would make his sujood about as long as his rukoo', and sometimes he would make it extremely long due to the circumstances, as one of his Companions said: "The Messenger of Allaah (sallallaahu 'alaihi wa sallam) came out to us for one of the two later prayers, [Zuhr or 'Asr,] carrying Hasan or Husain. The Prophet (sallallaahu 'alaihi wa sallam) then came to the front and put him down [next to his right foot], said takbeer for the prayer and commenced praying. During the prayer, he performed a very long prostration, so I raised my head [from among the people], and there was the child, on the back of the Messenger of Allaah (sallallaahu 'alaihi wa sallam), who was in prostration. I then returned to my prostration. When the Messenger of Allaah (sallallaahu 'alaihi wa sallam) had offered the prayer, the people said, 'O Messenger of Allaah! In the middle of [this] your prayer, you performed a prostration and lengthened it so much that we thought either something had happened, or that you were receiving revelation!' He said, Neither of those was the case: actually, my son made me his mount, so I did not want to hurry him until he had satisfied his wish "128 

In another hadeeth, "He (sallallaahu 'alaihi wa sallam) was praying. When he performed sajdah, al-Hasan and al-Husain jumped onto his back. When the people tried to stop them, he gestured to them to leave the two alone. After offering his prayer, he placed them in his lap and said, Whoever loves me should love these two."129

• He would often prostrate on the (bare) ground.137 
• "His Companions would pray with him in the intense heat, so when one of them could not press his forehead against the ground, he would spread his robe and prostrate on that."138 
• He also used to say, the whole earth has been made a place of worship (masjid) and a purification for me and my ummah; so wherever prayer becomes due on someone of my ummah, he has his place of worship (masjid) and his purification next to him. Those before me used to think that this was too much: indeed, they would only pray in their churches and synagogues.139 
• Sometimes, he would prostrate in mud and water, and that happened to him once at dawn on the twenty-first night of Ramadaan, when it rained and the roof of the mosque, which was made of palm-branches, was washed away. So he (sallallaahu 'alaihi wa sallam) prostrated in mud and water; Abu Sa'eed al- Khudri said, "So I saw, with my own eyes, the Messenger of Allaah (sallallaahu 'alaihi wa sallam), with traces of mud and water on his forehead and nose."140 
• Also, "he would pray on a khumrah"141 sometimes, or "on a mat"142 sometimes, and "he prayed on it once when it had become blackened due to prolonged use."143

• "He (sallallaahu 'alaihi wa sallam) would raise his head from prostration while saying takbeer"144, and he ordered "the one who prayed badly" to do that, saying,
• The prayer of any person is not complete until ... he prostrates until his limbs are at rest, then he says, 'Allah is the Greatest' and raises his head until he is sitting straight.145 Also, "he would raise his hands with this takbeer" sometimes.146 

Sitting between the Two Sajdahs:

"He would lay his left foot along the ground and sit on it [relaxed]"147, and he ordered "the one who prayed badly" thus, saying to him, When you prostrate, prostrate firmly, then when you rise, sit on your left thigh.148
"He would have his right foot upright"149, and "point its toes towards the qiblah."150

Iq'aa'Between the Two Sajdahs:

"He would sometimes practise iq'aa' [resting on both his heels and (all) his toes]."151

Lengthening the Sitting between the Two Sajdahs:

Also, "he would lengthen it until it was about almost as long as his sajdah"154, and sometimes, "he would remain (in this position) until one would say: He has forgotten."155    

The Adhkaar between the Two Sajdahs:

In this sitting, he (sallallaahu 'alaihi wa sallam) would say: 

1. O Allaah! (in one version: O my Lord!) Forgive me; have mercy on me; [strengthen me;] [raise my rank;] guide me; [pardon me;] sustain me.156 Or sometimes, he would say: 
2. O my Lord! Forgive me, forgive me.157 

He would say the above two in night prayer also.158

The Obligation of Being at Ease between the Two Sajdahs

"He (sallallaahu 'alaihi wa sallam) would be relaxed until every bone returned to its (proper) position" (152), and he ordered "the one who prayed badly" likewise, and said to him, The prayer of any of you is not complete until he does this. (153)

"He would say takbeer and prostrate for the second time."159 He also ordered "the one who prayed badly" to do so, saying to him after he had ordered him to be at ease between sajdahs, then say 'Allaah is the Greatest' and prostrate until your joints are relaxed [and do that in all your prayer].160 He would perform this sajdah exactly as he performed the first one. Also, "he would raise his hands with this takbeer" sometimes.161

Next, "he would raise his head while saying takbeer"162, and he ordered "the one who prayed badly" to do likewise, saying to him after ordering him to prostrate for the second time, "then raise your head and say takbeer"163. He also said to him, "[then do that in all your bowings and prostrations,] for if you do that, your prayer will be complete, and if you fall short in any of this, you will be deficient in your prayer."164 Also, "he would raise his hands"165 sometimes with this takbeer.

The Sitting of Rest:

Next, "He would sit straight [on his left foot, upright, until every bone returned to its position]."166