An excerpt from "Got Questions.org" entitled, "Why is " You shall not murder" in the Ten Commandments?" states: "What is murder in God’s eyes? From the human perspective, murder is the physical act of taking another’s life. However, we also must consider that God defines murder as any thought or feeling of deep-seated hatred or malice against another person. In other words, it is more than just a physical act that constitutes murder to God, who tells us that “everyone who hates his brother is a murderer, and you know that no murderer has eternal life abiding in him” (1 John 3:15 ESV). When we harbor hatred in our hearts for another, we have committed the sin of murder in God’s eyes. The disdain towards another person never has to be demonstrated outwardly because God looks upon the heart for the truth (1 Samuel 16:7; Matthew 15:19). As Christians and as human beings, we know that unjustified killing is wrong. God’s Word is very clear on this point: “You shall not murder.” And what God says we must obey, or we face the consequences on judgment day." This article may be viewed at: Why is "You shall not murder" in the Ten Commandments?/gotquestions.org
Reference: Romans 13:9