Idolatry: Consists in Swearing by Other Gods
Source: TTT
Exodus 23:13
Pay close attention to everything I have said to you. You must not invoke the names of other gods; they must not be heard on your lips.
Joshua 23:7
So you are not to associate with these nations that remain among you. You must not call on the names of their gods or swear by them, and you must not serve them or bow down to them.