When tadyatha appears in the middle of a mantra, what is its function? It seems to be dividing the mantra into 2 parts. For example, in the long medicine Buddha mantra and the Cundi mantra:
namaḥ saptānāṁ samyak-saṁbuddha koṭīnāṁ
tad-yathā oṁ cale cule cundi svāhā
namo bhagavate bhaiṣajyaguru
vaiḍūryaprabharājāya tathāgatāya
arhate samyaksambuddhāya tadyathā:
oṃ bhaiṣajye bhaiṣajye mahābhaiṣajya-samudgate svāhā

