Undoubtedly, He is among Our most dignified fully believing devotees.
He is one of our believing servants.
He was one of Our believing worshipers
Surely he was one of Our believing servants
That he truly is from Our worshippers/slaves the believers
Abraham was indeed one of My believing servants
He is indeed one of Our high ranking, firmly believing bondmen
Surely, he was one of our believing servants
Surely, he was of Our servants with (perfect faith)
Surely, he was (one) of Our believing servants
Verily, he was one of Our believing slaves