Pope Francis warned in his homily Thursday that envy, greed, and hate in the heart will breed war, violence, and murder in the world.  

"War begins in here and finishes out there. The news we see in the papers or on television… Today so many people die, and that seed of war, which breeds envy, jealousy, and greed in my heart, is the same – grown up, become a tree – as the bomb which falls on a hospital, on a school, and kills children," said the Pope in a reflection of the damage of war during morning Mass at the chapel of Casa Santa Marta Feb. 16.

Drawing from the story in Genesis of the dove returning to Noah after the flood, the Pope said God gave the rainbow and the dove to demonstrate his promise and desire for peace to reign in the world among every people. But he said the signs also represent how fragile peace can be.

He said the dove is "a sign of what God desired after the flood: peace, that is, that all would live in peace…The dove and the rainbow are fragile. The rainbow is beautiful after a storm, but then a cloud comes and it disappears."

God's covenant is strong, but our commitment to it is weak, he said in reference to the example of Cain and Abel.

"The Covenant which God makes is strong, but we accept it in weakness. God makes peace with us but it is not easy to care for peace. It is a daily task, because within each of us is that seed of original sin, that is, the spirit of Cain which – for envy, jealousy, greed, and the desire to dominate – leads to war."

Pope Francis maintained that the responsibility of peace falls on every person; that we "are our brothers' keeper, and when there is blood spilt, there is sin, and God will demand an accounting… of the blood of our brothers and sisters who are suffering war."

"In today's world there is blood being spilt. Today the world is at war. Many brothers and sisters are dying, even innocent people, because the great and powerful want a larger slice of the earth; they want a little more power, or they want to make a little more money on arms trafficking," he said, citing the current proxy wars and conflicts fueled by weapon dealers.

Every man is a delegate of peace and has an obligation to ensure less blood is spilled in the future, he said referring to how war first festers in homes with families and friends.

"How do I care for peace in my heart, in my interior, and in my family? Care for peace; not only care for it but make it with your hands every day. Just so will we succeed in spreading it throughout the whole world."

Pope Francis gave a childhood story in which his mother and their neighbor rejoiced at the end of a war; how both woman cried tears of joy while sirens in their Argentine town declared peace.

He concluded the homily with a prayer for a grace of peace in our daily lives.

"May the Lord give us the grace to say: 'War is finished...War is finished in my heart; war is finished in my family; war is finished in my neighborhood; war is finished in my workplace; war is finished in the world.' In this way shall the dove, rainbow, and Covenant be strengthened."