Prostration of thanksgiving after every mandatory prayer was the practice ( Sunnat e Muwakkida) of the Prophet ( a.s.). Imam Jafar e Sadiq (a.s.) has hinted at it’s being mandatory and said that when a person makes a prostration of thanksgiving, Allah addresses the angels and tells them that a sincere creature is doing the Sajda e Shukr. He asks the angels to suggest what Reward must be given to the person. The angels would suggest that Allah keep His Blessings with the...