The Compendium of Caraka 1.27.138

1.27.138

bilvaṃ tu durjaraṃ pakvaṃ doṣalaṃ pūtimārutam/
snigdhoṣṇatīkṣṇaṃ tadvālaṃ dīpanaṃ kaphavātajit//

Bael fruit, however, when ripe is hard to digest, aggravates doṣas, and causes foul-smelling wind; / young, it is unctuous, hot, penetrating, kindles digestion, and overcomes kapha and wind.