The seventh beatitude reads "Blessed are the peacemakers, For they shall be called sons of God" (Matt. 5:9; NKJV). "Peace" (Hebrew "shalom") in the Bible is not just the mere absence of strife or warfare. It is rather a state of rest that results when all needs have been met and everything is in a state of equilibrium. At one point David asked the question, "Who is the man who desires life, And loves many days that he may see good?" (Ps. 34:12). The answer is given is this: "Keep your tongue from evil, And your lips from speaking deceit. Depart from evil and do good; Seek peace and pursue it" (vv. 13,14). Peace brings happiness and a sense of well-being; strife brings misery and anxiety. God wants us to be peacemakers.
War, on the other hand, is the most egregious manifestation of human evil. All the bonds of civility are broken loose, as nations pour themselves into an orgy of mutual destruction, with a wanton disregard for human life. In modern times science has given us many technical advances, but it has not changed human nature, and we now wage war against each other with weapons of mass destruction. We are cavemen armed with nukes.
We have a right to self-defense, and one of the primary functions of government is the protection of the lives and property of its citizens. But if everyone were righteous wars would not happen at all. We would all live at peace with one another. And in the kingdom of heaven there will be no war. "They shall beat their swords into plowshares, And their spears into pruning hooks; Nation shall not lift up sword against nation, Neither shall they learn war anymore" (Mic. 4:3).
"Blessed are the peacemakers, For they shall be called sons of God."
This, then, is what is involved in repentance. First we must humble ourselves before God and come to Him in genuine sorrow for our sin, asking for forgiveness. Then we must manifest a change of life. We must long for righteousness and a pure heart. We must be gentle and kind. We must be peacemakers. Only such can enter the kingdom of heaven.