"When we realize that we harbor within ourselves the desire to attack someone because they are weak, we have no doubt: It is the devil. Because attacking the weak is the work of Satan," the Pope said in his homily Jan. 8 at morning Mass in the Domus Sanctae Marthae.

The Pope centered his homily on the day's reading from the First Book of Samuel, which recounts the verbal abuse Hannah endured because she was unable to conceive a child.

Similar accounts in other Bible stories -- from Abraham's wife Sarah ridiculed by her servant to Job who was rejected by his wife after his misfortune -- are stories that Christians should take time to reflect on, the Pope said.

"I ask myself: What is within these people? What is it within us that pushes us to mock and mistreat others weaker than we are?" the Pope asked.

"It is understandable when a person resents someone stronger than them, perhaps because of envy … but toward the weak? What makes us do that? It is something habitual, as if I need to ridicule another person to feel confident; as if it were a necessity," he said.

Pope Francis said that as a child there was a woman named Angelina in his neighborhood and she was constantly ridiculed by others, especially children, because of her mental illness.

While people would generously give her food and clothes, local children would make fun of the woman and say, "Let's find Angelina and have some fun," the Pope said.

"Today we see it constantly in our schools -- the phenomenon of bullying, attacking the weak because 'you're fat or foreign or because you're black,'" he said. "This means there is something within us that makes us act aggressively toward the weak."

Although psychologists may give a different reason as to why some are inclined to bully the weak, Pope Francis said he believed it was "a consequence of original sin" and the work of Satan who "has no compassion."

"Let us ask the Lord to give us the grace of God's compassion," the Pope said. "He is the one who has compassion on us and helps us to move forward."