Charak Samhita
इन्द्राग्नी चाश्विनौ चैव स्तूयन्ते प्रायशो द्विजैः। स्तूयन्ते वेदवाक्येषु न तथाऽन्या हि देवताः ॥४८॥
Indra, Agni and Ashwins were worshipped mostly by the twin born and are praised in the vedic hymns, not so the other gods.
english translation
indrAgnI cAzvinau caiva stUyante prAyazo dvijaiH। stUyante vedavAkyeSu na tathA'nyA hi devatAH ॥48॥
hk transliteration by Sanscript