What is a Christian? Christians can be described from many angles, but from what we have said it is clear that we can cover everything by saying: True Christians are people who acknowledge and live under the word of God. They submit without reserve to the word of God written in “the Book of Truth” (Dan 10:21), believing the teaching, trusting the promises, following the commands. Their eyes are upon the God of the Bible as their Father and the Christ of the Bible as their Savior.
Christians will tell you, if you ask them, that the Word of God has both convinced them of sin and assured them of forgiveness. Their consciences, like Luther’s, are captive to the Word of God, and they aspire, like the psalmist, to have their whole lives brought into line with it. “Oh, that my ways were steadfast in obeying your decrees!” “Do not let me stray from your commands.” “Teach my your decrees. Let me understand the teaching of your precepts.” “Turn my heart toward your statutes.” ” May my heart be blameless toward your decrees” (Ps 119:5, 10, 26-27, 36, 80). The promises are before them as they pray, and the precepts are before them as they go about their daily tasks.

-J.I. Packer, Knowing God, pg 116