it is a fact too frequently overlooked that in the NT the most characteristic terms that refer to sanctification are used, not of a process, but of a once-for-all definitive act.
The key passage for Murray is R6:1-7:6. I'm not sure how those who persist in referring to Christians as 'sinners' reconcile this passage to their position. For Murray,
compelled to take account of the fact that the language of sanctification is used with reference to some decisive action that occurs at the inception of the Christian life, and one that characterizes the people of God in their identity as called effectually by God's grace.
there is no possibility of toning down the antithesis.And, its not just Paul, but Peter too. In both 1P2 and 1P4 the same thought appears. Oh yes, John does it too - 1J3. Murray concludes,
The person begotten of God does righteousness, loves and knows God, loves those who are begotten of God, and keep the commandments of God.