If one enters the mosque and the imam has already risen from bowing, and he does not know whether it is the last rak'ah or not, does he join him?

The questioner:
Honorable Shaykh, may Allah grant you success, a man entered the mosque and the imam had already risen from bowing, and he did not know whether this rak'ah was the last one or not? The question is: does he join the imam, or does he wait to be sure?

The Shaykh:
If he has not...

The questioner:
And the imam has risen from bowing, and he does not know whether this is the imam's last rak'ah or not?

The Shaykh:
If he does not know, he joins him. If he does not know, he joins him. But if he knows that this is the last rak'ah and he knows that people are coming to pray and he is waiting for them, then when the imam says the taslim, they establish the prayer and he prays. But if no one informs him, or he does not know that this is the last one, then he joins them, praise be to Allah, and he does not waste his time, nor does he miss the reward and virtue in joining them. Yes.