The Compendium of Caraka 3.1.25

3.1.25

tasya sādguṇyamupadekṣyāmaḥ --- uṣṇamaśnīyāt; uṣṇaṃ hi bhujyamānaṃ svadate, bhuktaṃ cāgnimaudaryamudīrayati, kṣipraṃ jarāṃ gacchati, vātamanulomayati, śleṣmāṇaṃ ca parihrāsayati&; tasmāduṣṇamaśnīyāt//

We shall teach the excellence thereof: one should eat warm [food]; for warm [food], when being eaten, is savory, and when eaten, stimulates the digestive fire of the stomach, undergoes digestion quickly, causes vāta to move downward, and reduces kapha; therefore, one should eat warm [food].