The World Federation One Stop Fiqh

Ruling 1389

One can follow the imam of a congregational prayer who is performing the qaḍāʾ of his own or someone else’s daily prayer about which he is certain. However, if he is performing such a qaḍāʾ prayer as a precautionary measure [as opposed to being certain about it being a qaḍāʾ prayer], then it is not permitted to follow him unless the follower is also performing his prayer as a precautionary measure and the reason for his precaution is the same as that of the imam’s;48 and if the follower has another reason for his precaution as well, he can still follow.

48 For example, the imam and the follower have deemed it probable that the place where they both performed a previous prayer was usurped, and so they are now performing that prayer again as a precautionary measure.