The Compendium of Bheḷa 3.3.3

3.3.3

kadācitpacyate bhuktaṃ kadācinna vipacyate | guru vā laghu vā yasya viṣamāgniḥ sa ucyate ||

In whom what is eaten sometimes digests and sometimes does not digest, / whether heavy or light: he is said to have an irregular digestive fire.