Answered by Ustadha Shazia Ahmad
Is it compulsory to say subhana rabbial azim wa bihamdihi in the Ruku state in prayer while been lead by an Imam? Or do we say subhana rabbial azim and how many times? Some say we don’t have to say it. And they further said if we say it once, it is fard, twice is sunnah and thrice is mustahabb.
In prayer that one is praying alone, or is an imam, or a follower, it is not obligatory to say the above-mentioned dhikr in the bowing position, rather it is sunna. It is a sunna to say it three times and that is the least optimal number. If one is praying alone, or one is an imam who has followers that don’t mind the extra dhikr, one may say it five, seven, nine or eleven times. (Reliance, f8.30)
This dhikr is merely recommended and they don’t have different degrees as mentioned in the question.
And Allah knows best.
Shazia Ahmad