The criterion for combining two prayers due to rain

The questioner:
Honorable Shaykh, we received this question. He says: Some of the imams of the mosques, when it rains, combine the Maghrib and 'Isha' prayers. Some of them combine when the first drops of rain fall, while others do not combine at all. What is the criterion for this?

The Shaykh:
Both are wrong: the one who combines merely for a light sprinkle, and the one who does not combine at all, even in heavy rain. Both are wrong, but the first is more severe, the one who combines without a reason for combining. This is because the default is that each prayer is performed in its own time, and they are not combined except for a valid legal excuse. Among these excuses is heavy rain that wets the clothes or leaves mud on the road. This is what justifies combining. As for a mere light sprinkle, this does not permit combining, and the second prayer is not valid before its time. And the second question

The questioner:
Yes, he says: Some mention the criterion, O Shaykh, regarding the Friday prayer.

The Shaykh:
We mentioned it. We mentioned the criterion. Yes. Yes.