SB 9.9.28
deho ’yam manuso rajan
purusasyakhilarthadah
tasmad asya vadho vira
sarvartha-vadha ucyate
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
O King, O hero, this human body is meant for universal benefits. If you kill this body untimely, you will kill all the benefits of human life.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Srila Narottama dasa Thakura has sung:
hari hari viphale janama gonainu
manusya-janama paiya, radha-krsna na bhajiya,
janiya suniya visa khainu
The body of a human being is extremely valuable because in this body one can understand the instructions of Krsna and attain the ultimate destination of the living entity. The living entity is within the material world to fulfill the mission of going back home, back to Godhead. In the material world, one hankers for happiness, but because one does not know the ultimate destination, one changes bodies one after another. However, if one gets the opportunity to possess a human form of body, in this body he can fulfill the four principles of dharma, artha, kama and moksa, and if one is properly regulated he makes further progress, after liberation, to engage in the service of Radha and Krsna. This is the success of life: to stop the process of repeated birth and death and go back home, back to Godhead (mam eti), to be engaged in the service of Radha and Krsna. Therefore, taking a human body is meant for completing one’s progress in life. Throughout human society, killing of a human being is taken very seriously. Hundreds and thousands of animals are killed in slaughterhouses, and no one cares about them, but the killing of even one human being is taken very seriously. Why? Because the human form of body is extremely important in executing the mission of life.