While followers of Jesus do good, not to gain salvation but because we have been saved, we can know that our good deeds will be rewarded.
God does not give to those whom He has saved, what they justly deserve - eternity in hell.
He does give punishment to those who persist in evil because He is Just.
He does give good for evil, because He is good.
He does give good for good because His grace and mercy endure forever.
He will never give punishment for good because He is not unjust.
He will give punishment for evil and He will give grace for evil to those of His own pleasing.