Hadith.1199 - Al-Halabi narrated from Imam Jafar ibn Muhammad Al-Sadiq عليه السلام that He said:
"If you miss a part of the prayer with the Imam, consider what you perform upon joining as the beginning of your prayer, and do not consider the beginning of your prayer as its end”.
If the Imam makes you sit at a place where you should stand, you should sit lightly (without fully resting) and not sit in a fully settled manner.
