A group from amongst the former ones.
Many from the early generations.
a multitude of the ancients
A multitude from among the first
A group from the first/beginners
The right side people will be those …
A large group from the earlier generations
A large party from among the first believers
A large group of them will be from the earlier people
(This group will consist of) a large party from the earlier people (of Islam)
A multitude of those (on the Right Hand) will be from the first generation (who embraced Islam)