When Jesus had cast out a devil, some of the people said, ‘It is through Beelzebul, the prince of devils, that he casts out devils.’ Others asked him, as a test, for a sign from heaven; but, knowing what they were thinking, he said to them, ‘Every kingdom divided against itself is heading for ruin, and a household divided against itself collapses. So too with Satan: if he is divided against himself, how can his kingdom stand? – since you assert that it is through Beelzebul that I cast out devils. Now if it is through Beelzebul that I cast out devils, through whom do your own experts cast them out? Let them be your judges then. But if it is through the finger of God that I cast out devils, then know that the kingdom of God has overtaken you. So long as a strong man fully armed guards his own palace, his goods are undisturbed; but when someone stronger than he is attacks and defeats him, the stronger man takes away all the weapons he relied on and shares out his spoil.
‘He who is not with me is against me; and he who does not gather with me scatters.
‘When an unclean spirit goes out of a man it wanders through waterless country looking for a place to rest, and not finding one it says, “I will go back to the home I came from.” But on arrival, finding it swept and tidied, it then goes off and brings seven other spirits more wicked than itself, and they go in and set up house there, so that the man ends up by being worse than he was before.’
Source: Jerusalem Bible
Catechism of the Catholic Church
385 God is infinitely good and all his works are good. Yet no one can escape the experience of suffering or the evils in nature which seem to be linked to the limitations proper to creatures: and above all to the question of moral evil. Where does evil come from? “I sought whence evil comes and there was no solution”, said St. Augustine, and his own painful quest would only be resolved by his conversion to the living God. For “the mystery of lawlessness” is clarified only in the light of the “mystery of our religion”. The revelation of divine love in Christ manifested at the same time the extent of evil and the superabundance of grace. We must therefore approach the question of the origin of evil by fixing the eyes of our faith on him who alone is its conqueror.
For the leader; according to Muth Labben. A psalm of David.
I will praise you, LORD, with all my heart; I will declare all your wondrous deeds.
I will delight and rejoice in you; I will sing hymns to your name, Most High.
For my enemies turn back; they stumble and perish before you.
You upheld my right and my cause, seated on your throne, judging justly.
You rebuked the nations, you destroyed the wicked; their name you blotted out for all time
The enemies have been ruined forever; you destroyed their cities; their memory has perished.
The LORD rules forever, has set up a throne for judgment.
It is God who governs the world with justice, who judges the peoples with fairness.
Source: The New American Bible