The correct answer to this open question is the following.
The two texts that McQuilkin and Copan point to as important for consideration before discussing the roles of church and state were Matthew 7 and Matthew 22.
Robertson McQuilkin and Paul Copan are the authors of the book "An Introduction to Biblical Ethics: Walking in the Way of Wisdom." These authors tried to answer difficult questions such as how a human can differentiate from good and bad behavior in the eyes of God. They tried to find an answer for the purpose of humans in this existence and if humans can thrive without the help of God. In the text, the authors also establish that the roles of the church and the roles of the state are completely different and always have to be separated.
