The Pope focused his homily on the day's first reading (1 Sm 18: 6-9; 19: 1-7) in which Saul plots to kill David out of jealousy for his growing fame. Although Saul heeded his son's advice to not murder David, the Pope said, his jealousy returned like a "sickness" that opened the door to envy.

"Envy is an ugly thing! It is an attitude, an ugly sin," he said. "And jealousy or envy grows in the heart like a bad weed: It grows, but does not let the grass grow."

One who has an envious heart, he continued, cannot find peace and is tormented. The Pope noted that because of Satan's envy, "death entered into the world."

"Envy kills and it cannot tolerate that someone has something that I don't have," he said. "And he is always suffering because the heart of someone jealous or envious suffers. It is a suffering heart."

The Pope called on Christians to pray for the grace to not open their "hearts to jealousy, to not open the heart to envy because these things always lead to death."

Envy, he added, was also "the instrument" used by the high priests and scribes to deliver Jesus to Pontius Pilate and be put to death.

"Let us also ask the Lord for the grace to never deliver to death a brother, a sister of the parish, of the community, not even a neighbor because of envy," Pope Francis said. "Each one has their sins, each one has their virtues; they are specific to each one. Look for the good and do not kill (others) with gossip out of envy or jealousy."