My drill sergeant used to constantly yell, “It would behoove you all to remember this!!” I’ll apply that phrase to Murray’s fine note on Romans 3.21.
“Law in one sense pronounces the opposite of justification [i.e. condemnation], the law in another sense preaches justification. This illustrates the necessity in each case of determining the precise sense in which the term ‘law’ is used by the apostle and we must not suppose that the term always has the same denotation and connotation. Exposition has suffered from failure to recognize this variation.”
Quote taken from page 110 of John Murray, The Epistle to the Romans (Grand Rapids: Eerdmans, 1997).
Side note — for more on connotation and denotation, see pages 45-47 of Peter Cotterell and Max Turner, Linguistics and Biblical Interpretation (Downers Grove: InterVarsity Press, 1989).