Charak Samhita
अन्येद्युष्को द्व्यहग्राही तृतीयकचतुर्थकौ। स्वे स्वे काले प्रवर्तन्ते काले ह्येषां बलागमः ॥११३॥
Diseases like anyedyushka (quotidian fever which occurs at a fixed time every day), dvyahagrahi (reverse quotidian fever), tritiyaka (tertian fever which occurs at an interval of one day) and chaturthaka (quartan fever which occurs at an interval of two days) manifest themselves at fixed hours in as much as they get strength only at such hours.
english translation
anyedyuSko dvyahagrAhI tRtIyakacaturthakau। sve sve kAle pravartante kAle hyeSAM balAgamaH ॥113॥
hk transliteration by Sanscript