Sunan Abi Dawud 4344
سنن أبي داود#4344SahihNarrated AbuSa'id al-Khudri: The Prophet (ﷺ) said: The best fighting (jihad) in the path of Allah is (to speak) a word of justice to an oppressive ruler
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Zubair Ali ZaiHasan
In-book reference: 39:54