Sunan an-Nasa'i #4209 · The Book of al-Bay'ah

Sunan an-Nasa'iIt was narrated from Tariq bin Shihab that
Sunan an-Nasa'i · Book 39 · The Book of al-Bay'ah
Sunan an-Nasa'i · كتاب 39 · كتاب البيعة
a man asked the Prophet, when he had put his leg in the stirrup: "Which kind of Jihad is best?'" He said: " a word of truth spoken before an unjust rulers
أَخْبَرَنَا إِسْحَاقُ بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ، عَنْ سُفْيَانَ، عَنْ عَلْقَمَةَ بْنِ مَرْثَدٍ، عَنْ طَارِقِ بْنِ شِهَابٍ، أَنَّ رَجُلاً، سَأَلَ النَّبِيَّ صلى الله عليه وسلم وَقَدْ وَضَعَ رِجْلَهُ فِي الْغَرْزِ أَىُّ الْجِهَادِ أَفْضَلُ قَالَ ‏
"‏ كَلِمَةُ حَقٍّ عِنْدَ سُلْطَانٍ جَائِرٍ ‏"‏ ‏.‏
Reference : Sunan an-Nasa'i 4209In-book reference : Book 39, Hadith 61