Sayyiduna Adi bin Hatim (may Allah be pleased with him) said: I came to the Prophet (peace and blessings be upon him) with a cross of gold around my neck. He said: I heard the Messenger of Allah (peace and blessings be upon him) saying: "They took their scholars and monks as lords besides Allah." [Surah al-Tawbah: 31]
I said: O Messenger of Allah, they did not worship them. He (peace and blessings be upon him) said: "Yes, but they declared lawful for them what Allah had made unlawful for them, and declared unlawful for them what Allah had made lawful for them. That was their worship of them."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20350