In the last sentence of verse فَأُولَـٰئِكَ لَهُمْ جَزَاءُ الضِّعْفِ بِمَا عَمِلُوا وَهُمْ فِي الْغُرُفَاتِ آمِنُونَ (Therefore, such people will have the double reward for what they did, and they will be at peace in the upper chambers (of Paradise). - 34:37), mentioned there is the state of the people of 'Iman (faith) and good deeds for they are the ones acceptable with Allah. Whether or not they are recognized in this world, their return in the Hereafter will be double or manifold. The word: ضِعف (di` f) with a kasrah of the letter: (dad) is a verbal noun which means 'like a thing' or 'the likes of a thing'. The sense is that the way wealthy people keep amassing their wealth in the worldly life, Allah Ta’ ala would increase the return for His accepted people in the Hereafter many times over. For example, the return for one deed would be ten of its likes, or ten times as much. Then, it is not so restricted either. Granted the person's sincerity in deed and in view of other causes and considerations, the return of one such deed can go up to seven hundred times. That returns at this high scale would also be given as stands proved from Sahih ahadith. It is interesting that this too is not restricted. It could be more than that. In short, these people of faith and good deed shall be residing in the elevated chambers of Paradise in perfect peace and forever shielded against all sorrows.
The word: غُرُفَات (ghurufat) is the plural form of: غُرفَۃ (ghurfah). It denotes a part of the mansion considered distinct and high as compared to other parts.