Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: "When the Prophet (peace and blessings be upon him) conquered Makkah, Iblis let out a cry and his armies gathered around him. He said: After this day of yours, give up hope of bringing the Ummah of Muhammad back to shirk; but put them to trial in their religion, and spread wailing (screaming and beating oneself over the dead) among them."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12266