Abu al-Hayyaj al-Asadi says: Ali bin Abi Talib (may Allah be pleased with him) said to me: "I am sending you on the same mission on which the Messenger of Allah (peace and blessings be upon him) sent me: 'Do not leave any raised grave without levelling it with the ground, nor any image in a house without effacing it.'"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6757