Abu Hurairah (May Allah be pleased with him) reported: Messenger of Allah (sallallaahu alayhi wa sallam) said, "On the Resurrection Day, the rights will be paid to those to whom they are due so much so that a hornless sheep will be retaliated for by punishing the horned sheep which broke its horns". [Muslim]
Commentary: This Hadith makes it abundantly clear that there will be utmost justice on the Day of Resurrection. So much so that Allah will redress even the grievance of the aggressed animals against the aggressors. Thus, this Hadith serves a severe warning for people. When animals, who are devoid of sense, will not be forgiven, how would mankind be, which is gifted with senses? The latter will not be pardoned if they are guilty of having been unjust to anyone without adequately compensating them.
Ref.: Imam Al-Nawawi's Riyad-us-Saliheen # 204.