Ramayana
अर्धस्य देवो वरदो वरार्धस्य तव ह्यहम् । तस्मादर्धं गृहाण त्वं स्त्रीपुंसोर्यावदिच्छसि ॥ 7-87-24 ॥
"The god is the bestower of one half of the boon, and I indeed am the bestower of the other half; therefore take from your half as much of womanhood or manhood as you wish."
english translation