Shiva Purana
किन्तु देवेश्वरो रुद्रः प्रसीदति महेश्वरः ॥ सुदुर्लभो मृत्युहीनस्तव पुत्रो ह्ययोनिजः ॥ १४ ॥
But if Śiva, the lord of the gods, becomes delighted, even an immortal son not born of a womb, though hard to get, may be obtained.
english translation
kintu devezvaro rudraH prasIdati mahezvaraH ॥ sudurlabho mRtyuhInastava putro hyayonijaH ॥ 14 ॥
hk transliteration by Sanscript