Shiva Purana
ततः शिवाज्ञया तस्मात्तासु राज्ञस्स्वयं हरिः ॥ चतुर्भिश्चैव रूपैश्चाविर्बभूव नृपात्मजः ॥ ३६ ॥
Then at the behest of Śiva, Viṣṇu himself was born of the ladies in four different forms.
english translation
tataH zivAjJayA tasmAttAsu rAjJassvayaM hariH ॥ caturbhizcaiva rUpaizcAvirbabhUva nRpAtmajaH ॥ 36 ॥
hk transliteration by Sanscript