A man asked the Prophet ﷺ, while the Prophet had already placed his foot in the stirrup, "Which jihad is best?"He replied, "A word of truth spoken before a tyrannical ruler."
أخبرنا إسحق بن منصور قال حدثنا عبد الرحمن عن سفيان عن علقمة بن مرثد
أن رجلا سأل النبي ﷺ وقد وضع رجله في الغرز أي الجهاد أفضل قال كلمة حق عند سلطان جائر
[Hasan] Ahmad reported it, 4/315, from Abdul-Rahman bin Mahdi through him, and it is in Kubra, no. 7834, and Diya Maqdisi mentioned it in Al-Ahadith Al-Mukhtarah. Sufyan Thawri used "an" in his transmission, and the hadith has corroborating narrations in Ibn Majah, no. 4012, and Abu Dawud, no. 4344, and others besides them.