They took their scholars and priests to be lords besides God, and the Messiah son of Mary, while they were only commanded to serve One god, there is no god but He, be He glorified for what they set up.
Translation endnotes
[9:30-31] The system of islam belongs to God alone (98:5). Accepting the fatwas of this or that cleric as islam is setting up partners with God. See 42:21. Also, see 2:59; 2:79; 5:41-44.