tasmād asya vadho vīra
Śrīla Narottama dāsa Ṭhākura has sung:
hari hari viphale janama goṅāinu
manuṣya-janama pāiyā, rādhā-kṛṣṇa nā bhajiyā,
jāniyā śuniyā viṣa khāinu
The body of a human being is extremely valuable because in this body one can understand the instructions of Kṛṣṇa 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, kāma and mokṣa, and if one is properly regulated he makes further progress, after liberation, to engage in the service of Rādhā and Kṛṣṇa. This is the success of life: to stop the process of repeated birth and death and go back home, back to Godhead (mām eti), to be engaged in the service of Rādhā and Kṛṣṇa. 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.