Biblical explanation
Jesus said: "Think not that I am come to send peace on earth: I came not to send peace, but a sword." Matthew 10:34 The next verses explain what He meant. The "sword" would divide families because some would accept Him while others rejected Him: "For I am come to set a man at variance against his father, and the daughter against her mother." Matthew 10:35 The context is therefore relational division caused by allegiance to Christ, not a command to take up weapons. Jesus consistently taught love for enemies: "Love your enemies, bless them that curse you." Matthew 5:44 When Peter later used an actual sword to defend Jesus, Christ told him: "Put up again thy sword into his place." Matthew 26:52 Jesus also said: "My kingdom is not of this world: if my kingdom were of this world, then would my servants fight." John 18:36 The "sword" of Matthew 10 therefore describes the divisive consequences of the gospel, not Christian violence. The New Testament instead describes the Christian's weapon as spiritual truth. Ephesians 6:17 calls God's Word "the sword of the Spirit." Jesus clearly predicted division because of Him. He did not instruct His disciples to spread Christianity through physical force.
Key takeaway
Salvation is entirely by grace through faith in Christ. His atoning sacrifice, heavenly ministry, and intercession are the foundation of assurance; obedience, Sabbath faithfulness, and loving service are the fruit of a redeemed life, never a way to purchase acceptance with God.