Muwatta Imam Malik (Riwayat Ibn al-Qasim)

And with the same chain of narration (it is narrated from Sayyiduna Ibn Umar, may Allah be pleased with them both) that a man called out to the Messenger of Allah, peace and blessings be upon him, and said: O Messenger of Allah! What is your opinion about the Dabb (monitor lizard)? So the Messenger of Allah, peace and blessings be upon him, said: "I neither eat it nor do I declare it unlawful."