This was said by the Blessed One, said by the Arahant, as I have heard:

"Bhikkhus, without directly knowing, without fully comprehending anger, with the mind not detaching from it, and without abandoning it, one is incapable of ending suffering. Indeed bhikkhus, by directly knowing, by fully comprehending anger, with the mind detaching from it, and by abandoning it, one is capable of ending suffering."

The Blessed One spoke on this matter. In this regard, it is said:

"Overcome by anger, through which, beings go to an unfortunate destination; Completely comprehending that anger, those seeing clearly abandon it; Having abandoned it, they do not return, to this world at any time."

This matter too was spoken by the Blessed One, as I have heard.