Explanation

A man who was set for travel asked the Prophet (may Allah's peace and blessings be upon him): Which type of Jihad is much rewarded? The Prophet (may Allah's peace and blessings be upon him) told him that it is to enjoin an oppressive ruler to do good or to forbid him from doing evil. Jihad is not restricted to fighting the disbelievers; rather, it has levels. The type mentioned in this Hadīth is the highest level in terms of reward, because it makes one vulnerable to being killed or imprisoned because of the ruler's injustice, or because it is seldom that someone takes it upon himself to undertake this perilous task.