Ruling on a traveler shortening the 'Isha' prayer behind someone praying Maghrib

Question:
I prayed Maghrib yesterday in an area a few meters after 'Arafah, then I walked until I got close to Muzdalifah. I found a group of non-Arabs wanting to pray, so I asked them if they would be praying Maghrib or 'Isha'? They did not understand, so I prayed with them intending 'Isha'. They prayed Maghrib, and when they stood up for the third unit, I sat down and said the closing salam. Is there any issue with that?

Answer:
This is a matter for consideration; because you prayed with them intending 'Isha' while they were praying Maghrib. Maghrib is not shortened, and 'Isha' is shortened. The most likely outcome, and the most apparent one, Allah knows best, is that the prayer is valid, because you intended it as 'Isha', and 'Isha' is shortened, while Maghrib is not shortened and does not take the place of 'Isha' in such a case. The most apparent and closest view, if Allah wills, is that you did it correctly. However, if it had been a four-unit prayer, it would have been obligatory for you to complete it with them. But the point is that this is sufficient, if Allah wills.