The stoic position is that virtue is it’s own reward.
Think about it for a couple of minutes, if you behaved badly whether there is a God or not, there’s still consequences for immoral actions and deeds, many of them are social, some are legal.
If you cause unnecessary suffering, you are automatically going to diminish the pool of people who otherwise might be willing to help you when you yourself are suffering and in need of help.
All philosophies share one thing in common and that it is not possible to go through life without enduring hardships in one form or another. There’s times when we all need help and support from our fellow human beings, be they friends, family or strangers.
Good deeds, create good consequences and good will from other human beings in exactly the same way that bad deeds and immoral actions cause bad consequences and bad will, hence my position that virtue is it’s own reward.
Being good is actually a form of self interest and self preservation.