Further to the above answers to your query;
1. Citation for the Emmet Fox quote;
Emmet Fox; “The Sermon on the Mount: The Key to Success in Life “
Copyright 1938 Published by Grosset & Dunlap
2.A PDF of this book (also containing “The Lord’s Prayer: An Interpretation” by Fox) can be found here; http://harrykatz.com/Sermon/Se..._The_Mount_eBook.pdf
3. A bit more of the text before the quote that Zendam has provided:
“It cannot be too often repeated that to entertain feelings of anger, resentment, jealousy, spite, and so forth, is certain to damage your health”
“For the same reason, to entertain negative emotions is to order trouble--quite independently of any seeming justification that you may suppose yourself to have”.
“I once came across an old sermon that was delivered in London during the French Revolution. The author, who took an extremely superficial view of the Gospel, said, referring to the Sermon on the Mount: "Surely it is justifiable to hate the Arch-butcher, Robespierre, and to execrate the Bristol murderer." This pronouncement perfectly illustrates the fallacy that we have been considering. To entertain hatred is ipso facto to involve yourself in certain unpleasant results, and, as far as you are concerned, it will not make the faintest shadow of a difference whether you are attaching the label “Robespierre” or “Tom” or “Dick” or Harry” to the emotion concerned. The question whether the man, Robespierre, was a demon or an angel of light, has nothing whatever to do with the matter.
To indulge in a sense of execration of anyone, (quite irrespective of any deserts, or otherwise, in the object of your condemnation) is certain to bring trouble on your own head proportionate to the intensity of the feeling you entertain, and the number of times or minutes that you devote to it. No Scientific Christian ever considers hatred or execration to be “justifiable” in any circumstances, but whatever your opinion about that might be there is no question about its practical consequences to you. You might as well swallow a dose of prussic acid in two gulps, and think to protect yourself by saying, “This one is for Robespierre; and this one for the Bristol murderer.” You will hardly have any doubt as to who will receive the benefit of the poison.”
4. Another quote with a similar idea;
Holding anger is a poison. It eats you from the inside. We think that hating is a weapon that attacks the person who harmed us. But hatred is a curved blade. And the harm we do, we do to ourselves.
~Mitch Albom; The Five People You Meet in Heaven; The Third Lesson
They have been at a great feast of languages, and stolen the scraps.