Second episode/adhyaya – Sankhya yoga
ya enaṁ vetti hantāraṁ
yaḥ—anyone; enam—this; vetti—knows; hantāram—the killer; yaḥ—anyone; ca—also; enam—this; manyate—thinks; hatam—killed; ubhau—both of them; tau—they; na—never; vijānītaḥ—in knowledge; na—never; ayam—this; hanti—kills; na—nor; hanyate—be killed.
Text Source – “http://prabhupadabooks.com/bg”
One who thinks that he is the killer or the one who thinks that he is being killed, both are not in knowledge. Because the Self(soul) can never be killed nor can kill anyone.
Both, the person who thinks that he is killing, and the person who thinks he is being killed, are not in knowledge.
If killing is not really killing, then can people kill anybody and think it’s not a sin?
Killing for dharma is not a sin. Arjuna was a warrior, it was his duty to kill the enemies and protect people. The closest I can relate to this, is the people in Army. They cannot say killing is sin and just sit and watch when the enemy attacks. May be killing, when the purpose for killing is based on dharma, and is within the boundaries of law, is okay.
But in any way soul cannot be killed.