It is narrated from Sayyiduna Kharashah bin al-Harith (may Allah be pleased with him), who was a Companion of the Prophet (peace and blessings be upon him), that the Prophet (peace and blessings be upon him) said: "None of you should be present with someone who is being killed while bound (helpless), for perhaps he is being killed unjustly, and then displeasure will descend upon them and he (the one present) will be struck by it along with them."
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 4166