Abu al-Bakhtari said: Sayyiduna Hudhayfah (may Allah be pleased with him) was asked about this verse: "They took their scholars and monks as lords besides Allah" [Surah al-Tawbah: 31]: Did they pray to them? He said: No. But they declared lawful for them what Allah had made unlawful for them, and declared unlawful what Allah had made lawful for them. Because of this they became lords.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20351