Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 21
Sanskrit:
एवं व्यवसितो राजन् भगवान् स महायशा: ।अस्तौषीदादिपुरुषमिलाया: पुंस्त्वकाम्यया ॥ २१ ॥
ITRANS:
evaṁ vyavasito rājanbhagavān sa mahā-yaśāḥastauṣīd ādi-puruṣamilāyāḥ puṁstva-kāmyayā
Translation:
Śukadeva Gosvāmī said: O King Parīkṣit, after the most famous and powerful Vasiṣṭha made this decision, he offered prayers to the Supreme Person, Viṣṇu, to transform Ilā into a male.