Mbh 5.195.3

“‘Bhishma continued, “Thus addressed by the Yaksha Sthuna, Sikhandin, O Bharata, came to his city, filled with great joy. And he worshipped with diverse scents and garlands of flower and costly presents persons of the regenerate class, deities, big trees and crossways. And Drupada, the ruler of the Panchalas, along with his son Sikhandin whose wishes had been crowned with success, and with also his kinsmen, became exceedingly glad. And the king then, O bull of Kuru’s race, gave his son, Sikhandin, who had been a woman, as a pupil, O monarch, to Drona. And prince Sikhandin obtained, along with yourselves, the whole science of arms with its four divisions. And (his brother) Dhrishtadyumna of Prishata’s race also obtained the same. Indeed, all this way represented unto me, O sire, by the spies, disguised as idiots and as persons without the senses of vision, and hearing whom I had set upon Drupada. It is thus, O king, that that best of Rathas, Sikhandin, the son of Drupada, having first been born a female, subsequently became a person of the other sex. And it was the eldest daughter of the ruler of Kasi, celebrated by the name of Amva, who was, O bull of Bharata’s race, born in Drupada’s line as Sikhandin. If he approacheth me bow in hand and desirous of fight, I will not look at him even for a moment nor smite him, O thou of unfading glory! Even this is my vow, known over all the world, viz., that I will not, O son of Kuru’s race, shoot weapons upon a woman, or one that was a woman before or one bearing a feminine name, or one whose form resembleth a woman’s. I will not, for this reason, slay Sikhandin. Even this, O sire, is the story that I have ascertained of Sikhandin’s birth. I will not, therefore, slay him in battle even if he approacheth me weapon in hand. If Bhishma slayeth a woman the righteous will all speak ill of him. I will not, therefore, slay him even if I behold him waiting for battle!”’