William Burkitt on Matthew 8:32

Although Christ seldom wrought any destructive miracle, and although he certainly foresaw that the swine would perish in the waters; yet that the people might see how great the power and malice of the devil would be, if not restrained by Christ, he permitted him to ever into the swine: Christ said unto them, Go; and how glad was Satan of this permission to enter into the swine, in order to their destruction.

Let it teach us our duty, by prayer to commit ourselves, and all that we have, morning and evening, into the hands of God's care; all that we have in the house, and all that we have in the field, that it may be preserved from the power and malice of evil spirits.