Abu Ja'far said: I was sitting with Sayyiduna Suwayd bin Muqarrin (may Allah be pleased with him) when he said: The Messenger of Allah (peace and blessings be upon him) said: "Whoever is killed resisting an injustice is a martyr."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6424