Abu Dawud Book 36, Hadith Number 4866.

Narated By Jabir ibn Abdullah AbuTalhah ibn Sahl al-Ansari : The Prophet (PBUH) said: No (Muslim) man will desert a man who is a Muslim in a place where his respect may be violated and his honour aspersed without Allah deserting him in a place here he wishes his help; and no (Muslim) man who will help a Muslim in a place where his honour may be aspersed and his respect violated without Allah helping him in a place where he wishes his help.