Here is a helpful observation from footnote 11 of Sam Waldron's introduction in Faith, Obedience, and Justification: Current Evangelical Departures from Sola Fide:
Any claim to believe in justification by faith alone is a claim to believe it in the sense in which it was held by that tradition. To claim to believe this doctrine, and yet tacitly depart from its classical articulation, is historically and practically misleading. To claim to believe in justification by faith alone and teach contrary to its meaning in the Reformation tradition is like claiming to believe in the Trinity while teaching Arianism or some other doctrine than that articulated by Athanasius, the Cappadocian Fathers, and Augustine.
Waldron articulates three distinctive features of justifying faith that define the doctrine in the Reformed tradition (as found in Luther, Calvin, and the Reformation confessions and catechisms). They are:
1. Justifying faith is defined as passive
2. A distinction (though not a separation) is maintained between justifying faith and obedience
3. A dichotomy, antithesis, or contrast is maintained between (the righteousness of) the law and (the righteousness of) the gospel