Is the prayer valid for a congregant who has performed ablution when following an imam who prayed with tayammum, and must it be repeated?

Summary

The majority of Hanafi, Maliki and Hanbali scholars permit a congregant with ablution to follow an imam who performed tayammum. In the Shafi'i school the ruling depends on the imam's situation: if the imam is not required to make up the prayer, such as tayammum while travelling or due to illness or injury, the congregant's prayer is valid and need not be repeated. If the imam is required to make up the prayer, such as a resident who finds no water where water is normally available or one using tayammum because of extreme cold, following him is not permitted and the congregant must repeat the prayer.

Written in our own words from the original fatwa — check the source before acting on it.