Valmiki Ramayana Ayodhya Kanda Sarga 39 Shloka 11

गुणवताम् of virtuous men, गुणानाम् of virtues, फलम् reward, एवम् this only, उच्यते is said, मन्ये I think, यत् since, साधुः pious man, वीरः heroic, पित्रा by father, मात्रा च by mother, वनम् to the forest, निर्वास्यते is being banished.

That the pious and heroic son is banished by his parents to the forest is, I think, the reward to the virtuous for his virtues.