Thou shalt not kill. Exodus 20:13
The Hebrew word for “kill” is “ratsach” which more specifically means to murder. Murder includes malice and self serving motives for killing. This commandment is clearly not forbidding capital punishment as that would conflict with the rest of the Bible. Whoso sheddeth man’s blood, by man shall his blood be shed. Genesis 9:6
In light of the cross all selfishness leads to murder. In John 8 Jesus says Satan was a murderer from the very beginning. In heaven Lucifer, now Satan, wanted the throne of God. Isaiah 14 The only way you get the throne is to eliminate the person on the throne. Many of the angels did not realize that Lucifer actually had murder on his mind while in heaven, but on the earth, at the cross, he did to God here on earth what he wanted to do to him in heaven-murder Him! The cross is where both Satan’s and God’s characters were manifested. At the cross we see Satan willing to kill anyone who gets in his way of getting what he wants, and we see God who is willing to die and say goodbye to life forever if He can just save someone else.
Self will always try to rise to the top and eliminate whoever gets in its way. This is why Christ took human nature to the cross and crucified self for us all. “God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh: That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.” Romans 8:3-4
I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me. Galatians 2:20
Love is being centered on the welfare of others. Hate, which leads to murder is being centered on self. The only way to overcome putting yourself first is to put others first. The only way to overcome hate is to love. So “Thou Shalt not kill” could actually be translated, “You will not put yourself first.” At the cross Jesus put others first. At the cross Satan put himself first, and showed the universe why he was a murderer from the very beginning, when he first started putting self first.