Charak Samhita
तत्रादौ सर्पिषः पानं कफपित्तोत्तरो न चेत्। दौर्बल्याद्देहधातूनां ज्वरो जीर्णोऽनुवर्तते ॥२९१॥
the patient in such case should be given ghee to drink provided kapha and pitta dosha are not aggravated. [Management of jeerna jwara (chronic stage)] The fever turns chronic if there is weakness in the tissues of the body.
english translation
tatrAdau sarpiSaH pAnaM kaphapittottaro na cet। daurbalyAddehadhAtUnAM jvaro jIrNo'nuvartate ॥291॥
hk transliteration by Sanscript