Attributed to Siddhartha Gautama, the Buddha
«Holding on to anger is like grasping a hot coal with the intent of throwing it at someone else; you are the one who gets burned.»
Misattributed
Verdict
It is not in Siddhartha Gautama, the Buddha's work
It does not appear in the canon. According to Bodhipaksa's research, it is a modern reworking of an image used by the commentator Buddhaghosa (5th century) in the Visuddhimagga, comparing the angry person to someone who picks up embers or excrement to strike another.
What they did say
Verified words of Siddhartha Gautama, the Buddha
«All that we are is the result of what we have thought: it is founded on our thoughts, it is made up of our thoughts. If a man speaks or acts with an evil thought, pain follows him, as the wheel follows the foot of the ox that draws the carriage.»
Dhammapada 1 (trad. inglesa de Max Müller, SBE X, 1881; texto pali en SuttaCentral)
«For hatred does not cease by hatred at any time: hatred ceases by love—this is an old rule.»
Dhammapada 5 (trad. inglesa de Max Müller, SBE X, 1881)
«Not to commit any sin, to do good, and to purify one's mind, that is the teaching of (all) the Awakened.»
Dhammapada 183 (trad. inglesa de Max Müller, SBE X, 1881)