The ruling on praying two congregations in one mosque

Question : A man says: A traveler entered a mosque on his way and found two congregations in it, and he did not know which one had been established first. What should he do? And is the prayer of the congregation that was established after the first one valid?

Answer : If he does not know, let him choose the one with the larger number of people, because that is better. As for those who established the second prayer, if they were ignorant, their prayer is valid. If they knew, there is a point of consideration regarding the validity of their prayer, unless the mosque does not have a regular imam, like the mosques that are on the roads; in that case, whoever enters prays. However, even so, it is not recommended that two congregations pray in one mosque.