Is the salam upon the Prophet in the tashahhud obligatory?

Question : Some people hold that the salam upon the Prophet (peace and blessings be upon him) in the tashahhud is obligatory only once, and that it remains recommended thereafter. I hope you will guide us on this matter?

Answer : Yes, the salam upon the Prophet (peace and blessings be upon him and his family) is obligatory in both the first and second tashahhud. However, in the first tashahhud, its obligation is one of obligation (wajib), not one of a pillar (rukn). If a person omits it, he performs two prostrations of forgetfulness before the taslim. As for its obligation in the second tashahhud, it is an obligation of a pillar, meaning that if a person omits it out of forgetfulness, he returns to his prayer, recites the tashahhud, and sends salam upon the Prophet (peace and blessings be upon him and his family). Yes. And he completes the tashahhud, then...