From Nagarjuna's Treatise on the Great Perfection of Wisdom
(Dharmamitra Translation)

For example, there once was a man who was a shrota-aapanna born into the family of a butcher. He was on the threshold of adulthood. Although he was expected to pursue his household occupation, he was unable to kill animals. His father and mother gave him a knife and a sheep and shut him up in a room, telling him, "If you do not kill the sheep, we will not allow you to come out and see the sun or the moon or to have the food and drink to survive."

The son thought to himself, "If I kill this sheep, then I will be compelled to pursue this occupation my entire life. How could I commit this great crime simply for the sake of this body?" Then he took up the knife and killed himself. The father and mother opened the door to look. The sheep was standing to one side whereas the son was laying there, already deceased.

At that time, when he killed himself, he was reborn in the heavens. If one is like this, then this amounts to not sparing [even one's own] life in safeguarding the integrity of the pure precepts. Ideas such as these constitute what is meant by the precept against killing.