Shiva Purana
एनमेव महामन्त्रञ्जीवानाञ्च तनुत्यजाम् ॥ काश्यां संश्राव्य मरणे दत्ते मुक्तिं परां शिवः ॥ ६२ ॥
It is this very mantra that Śiva speaks to individual souls who leave off their bodies at Kāśī to attain liberation hereafter.
english translation
enameva mahAmantraJjIvAnAJca tanutyajAm ॥ kAzyAM saMzrAvya maraNe datte muktiM parAM zivaH ॥ 62 ॥
hk transliteration by Sanscript