Shiva Purana
चन्द्रेण च तपस्तप्तं पण्मासं च निरंतरम् ॥ मृत्युंजयेन मंत्रेण पूजितो वृषभध्वजः ॥ ३९॥
The moon performed the penance incessantly for six months. He worshipped the bull-bannered deity with the Mṛtyuñjaya mantra.
english translation
candreNa ca tapastaptaM paNmAsaM ca niraMtaram ॥ mRtyuMjayena maMtreNa pUjito vRSabhadhvajaH ॥ 39॥
hk transliteration by Sanscript