Jami at Tirmidhi 280

Al-Bara said: When we performed Salat behind Allah's Messenger, he would raise his head from bowing, and no man among us would bend his back until Allah's Messenger prostrated, then we prostrated. ..

Ali narrated: Allah's Messenger said to me: 'O Ali! I love for you what I love for myself, and I dislike for you what I dislike for myself. Do not squat between prostrations.' ..

Tawus said: We asked Ibn Abbas about squatting (sitting) on the heels. He said: 'It is the Sunnah.' We said: 'We think that it is difficult for a man.' He said: 'Rather, it is Sunnah of your Prophet.' ..

Ibn Abbas narrated: Between the two prostrations, the Prophet would say: (Allahummaghfir li, warhamni, wajburni, wahdini, warzuqni). 'O Allah! Pardon me, have mercy on me, help me, guide me, and grant me sustenance.' ..

Ibn Abbas narrated: (Another chain) which is similar. ..

Abu Hurairah narrated: [Some of] the Companions of the Prophet complained [to the Prophet] about the hardship of the prostration on them, when they were so spread out, so he said: 'Use your knees.' ..