He was sitting with a group of the Prophet's ﷺ companions when the prayer of the Prophet ﷺ was mentioned. Abu Humayd al-Saidi said, "I was the most attentive among you to the prayer of the Messenger of Allah ﷺ." He then described the manner of the Prophet's ﷺ prayer, saying, "When he sat after the second rakah, he sat on his left foot and kept his right foot upright. When he sat in the final rakah, he placed his left foot forward, kept the other upright, and rested on his backside."
أنه كان جالسا مع نفر من أصحاب النبي ﷺ، فذكر صلاة النبي ﷺ فقال أبو حميد الساعدي: أنا كنت أحفظكم لصلاة رسول الله ﷺ، فذكر صفة صلاة النبي ﷺ ثم قال: فإذا جلس في الركعتين جلس على رجله اليسري، ونصب اليمني، وإذا جلس في الركعة الآخرة قدم رجله اليسرى ونصب الأخرى، وقعد على مقعدته.
Bukhari narrated it in the Book of Adhan (828) from Yahya bin Bukayr, who said, Layth told us, from Khalid (that is, bin Yazid), from Saeed (that is, Ibn Abu Hilal), from Muhammad bin Amr bin Halhala, from Muhammad bin Amr bin Ata, and he related the hadith. The hadith was already presented in detail in the chapter on raising the hands at the ruku and when rising from it.In this hadith there is evidence that in a prayer with two tashahhuds, the sitting posture in the first tashahhud differs from the sitting posture in the final one, since in the final one the sitting is on the buttocks, leaning to the left side. This is stated explicitly in the hadith of Yahya bin Saeed, who said, Abdul-Hameed bin Jafar told us, who said, Muhammad bin Amr bin Ata told me, from Abu Humayd, who said, "When the Prophet ﷺ was in the two rakats with which the prayer ended, he would draw back his left foot and sit on his side, leaning to one side, then give the salutation."Nasai narrated it (1262) from Yaqub bin Ibrahim Dawraqi and Muhammad bin Bashshar Bundar, and the wording is his, who both said, Yahya bin Saeed told us with this same account.Imam Ahmad held the same view, while Shafii took the general sense of his words "in the final rakat" to mean that the tashahhud of the Fajr prayer is like the final tashahhud in the four-rakat and three-rakat prayers. The forthcoming hadith of Ibn Masud points to this.