If a person joins Salah (Prayer) during the last Tashahhud (testification recited in the sitting position in the last unit of Prayer) before the Imam (the one who leads congregational Prayer) says Taslim (salutation of peace ending the Prayer), will they get the reward of offering congregational Salah
or will they get the reward of praying individually? What is the best course of action upon entering the Masjid (mosque) and finding the Imam in the last Tashahhud? Should one complete the Tashahhud or wait for others to come and pray with?
(Part No. 7; Page No. 321)
Anyone who joins the Imam during the last Tashahhud will not be considered to have caught the congregational Salah, but they will get the reward of whatever parts of Salah they pray with the Imam. To be considered having joined the congregational Salah, a latecomer should offer at least one Rak`ah (unit of Prayer) with the Imam. The Prophet (peace be upon him) said:
Anyone who catches one Rak`ah from Salah (in congregation) has caught the (congregational) Salah.
However, in the case stated by the questioner, it is better to join the Imam in Salah based on the purport of the Hadith:
Whatever (part of Salah) you arrive at, pray, and whatever (part) you have missed, make up for it.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.