(V.34:42) Almighty Allâh says: "They (Jews and Christians) took their rabbis and their monks to be their lords (by obeying them in things that they made lawful or unlawful according to their own desires without being ordered by Allâh) besides Allâh, and (they also took as their Lord) Messiah, son of Maryam (Mary), while they (Jews and Christians) were commanded [in the Taurât (Torah) and the Injeel (Gospel)] to worship none but one llâh (God - Allâh), Lâ ilâha illâ Huwa (none has the right to be worshipped but He). Praise and Glory is to Him, (far above is He) from having the partners they associate (with Him)." [The Qur’ân, Verse 9:31]
Once, while Allâh’s Messenger صلى الله عليه وسلم was reciting the above Verse, ‘Adi bin Hâtim said, "O Allâh’s Prophet! They do not worship them (rabbis and monks)." Allâh’s Messenger صلى الله عليه وسلم said, "They certainly do. They (i.e. rabbis and monks) made legal things illegal, and illegal things legal, and they (i.e. Jews and Christians) followed them, and by doing so they really worshipped them." [Narrated by Ahmad, At-Tirmidhi, and Ibn Jarir. (Tafsîr At-Tabarî, Vol.10, Page No.114)].