Sayyiduna al-Sa'ib (may Allah be pleased with him) relates: My family sent with me a bowl of milk and butter to their gods. I took it along, and I was afraid that if I ate anything from it (I would come to harm). I put it down, and then a dog came, drank the milk, ate the butter, and even urinated on the idol.
Al-Tabarani recorded it in al-Mu'jam al-Kabir, and its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الإيمان / 450