The ruling on sending blessings upon the Prophet in the final tashahhud and leaving it out

Question:
The questioner asks: Is sending blessings upon the Prophet (peace and blessings be upon him) in the second tashahhud obligatory? What is the ruling on the one who leaves it out, whether out of forgetfulness or intentionally? Is his prayer invalid?

Answer:
The prayer upon the Prophet (peace and blessings be upon him) in the final tashahhud is a pillar of the prayer. The prayer is not valid without it, and it is not dropped due to forgetfulness or ignorance. If he leaves it off, he has left off a pillar of the prayer. If he remembers it shortly after the taslim, he stands up and performs it. If he leaves it off out of forgetfulness or ignorance, and then remembers after the taslim, he returns and performs the tashahhud and the prayer upon the Prophet (peace and blessings be upon him) while sitting, then he prostrates two prostrations for forgetfulness, and then he says the taslim. However, if a long time has passed and he does not know until after a while, he repeats the entire prayer.

The presenter:
May Allah reward you,