Spinoza, Part 3, "Ethics"
Proposition XXXVIII: If a man has begun to hate a beloved thing, so that his love of it is altogether destroyed, he will for this very reason hate it more than he would have done if he had never loved it, and his hatred will be in greater proportion to his previous love.

Proposition XXXIX: If a man hates another he will endeavor to do him evil unless he fears a greater evil will therefore arise to himself; and, on the other hand, he who loves another will endeavor to do him good by the same rule.

Proposition XL: If we imagine that we are hated by another without having given him cause for it, we shall hate him in return.