It is reported from Sayyiduna Imam al-Hasan (may Allah be pleased with him) that he said: "O people, last night I saw something astonishing in a dream. I saw my Lord upon His Throne. Then the Prophet (peace and blessings be upon him) came and stood beside one of the legs of the Throne. Then Sayyiduna Abu Bakr (may Allah be pleased with him) came and placed his hand on the shoulder of the Prophet (peace and blessings be upon him). Then Sayyiduna Umar (may Allah be pleased with him) came and placed his hand on the shoulder of Sayyiduna Abu Bakr (may Allah be pleased with him). Then Sayyiduna Uthman (may Allah be pleased with him) came, and he was a little to one side. He said: 'O my Lord! Ask Your servants why they killed me.'" Sayyiduna Imam al-Hasan (may Allah be pleased with him) says: "Then two spouts of blood began to flow from the sky to the earth." The narrator says: It was said to Sayyiduna Ali (may Allah be pleased with him): "Have you not noticed what Sayyiduna Imam al-Hasan (may Allah be pleased with him) is narrating?" Sayyiduna Ali (may Allah be pleased with him) said: "He has narrated what he saw."
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 14561