Matthew 28:
18 And Jesus came up and spoke to them, saying, “All authority in heaven and on earth has been given to Me.
19 Go, therefore, and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit,
20 teaching them to follow all that I commanded you; and behold, I am with you always, to the end of the age.”
"Countless times I have heard Christians say, ‘Why do I need to study doctrine or theology when all I need to know is Jesus?’ My immediate reply is this: ‘Who is Jesus?’ As soon as we begin to answer that question, we are involved in doctrine and theology. No Christian can avoid theology. Every Christian is a theologian. . . . The issue for Christians is not whether we are going to be theologians but whether we are going to be good theologians or bad ones.”
-R. C. Sproul