Shiva Purana
यदा पुनः प्रजावृद्ध्यै ललाटाद्भवतो भवः ॥ उत्पन्नो ऽभूत्तदा त्वं मे गुरुः श्वशुरभावतः ॥ ३० ॥
When for multiplying the subjects, Śiva was born of your forehead you became my father-in-law and so elder to me.
english translation
yadA punaH prajAvRddhyai lalATAdbhavato bhavaH ॥ utpanno 'bhUttadA tvaM me guruH zvazurabhAvataH ॥ 30 ॥
hk transliteration by Sanscript