The ruling on separating from the imam in prayer for a valid religious excuse

Question:
May Allah reward you. This questioner says: I prayed Maghrib in a mosque that does not have a regular imam, and this was on my way to a lesson. The imam recited the qunut and prolonged it, and he included in the qunut for calamity things that do not belong to it, until I separated from him and completed the prayer alone so that I could catch the lesson. What is my obligation in this matter?

Answer:
If you intended to separate for a valid religious excuse, there is no harm in it. If you intended to separate for a valid religious excuse because something important would be missed, there is no harm. The one who separated from Mu'adh ibn Jabal in order to catch his donkeys—so that they would not be lost? The Messenger (peace and blessings be upon him) approved of that for him. If the intention to separate is for a valid purpose that would be missed, there is no harm.