Ma'mum abandoning saying Tashahhud while praying with the Imam

Q: A man offered Salah (Prayer) behind an Imam (leader of congregational Prayer), but he forgot to recite the last Tashahhud (testification recited in the sitting position in the last unit of Prayer) What is the ruling on his Salah? Is it invalid? What should he do?

A: As that person did not recite the last Tashahhud, his Salah is invalid, according to the strongest opinion of scholars. Because he omitted a Rukn (Pillar) in Salah, he must make up for it.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.