Shiva Purana
वरेणच्छंदयामास सा च वव्रे वरं तदा॥ पुत्रमिन्द्रवधार्थाय समर्थममितौजसम् ॥ ५ ॥
He flattered her with a boon and she then asked for a boon. A son of immeasurable prowess capable of killing Indra.
english translation
vareNacchaMdayAmAsa sA ca vavre varaM tadA॥ putramindravadhArthAya samarthamamitaujasam ॥ 5 ॥
hk transliteration by Sanscript