Riyad as-Salihin

'Aidh bin 'Amr (May Allah be pleased with him) reported: I visited 'Ubaidullah bin Ziyad and said to him: "Dear son, I heard Messenger of Allah (ﷺ) saying, 'The worst of rulers are those who treat their subjects harshly. Beware, lest you should be one of them."'

[Al-Bukhari].