Geerhardus Vos . . . says that the heart of legalism is when we separate the law of God from the person of God. And what we have got then are bare imperatives that don’t have an indicative that will sustain them. God Himself in His grace, love, kindness, and generosity was the indicative that would have sustained the imperative of “Don’t eat the fruit of this tree.” And I see that distortion of God’s character, and the notion of legalism that seeks to earn what now as fallen creatures we can never earn, and blinds us to His a priori love for us in Christ.
—Sinclair Ferguson, http://sovgracemin.org/Blog/post/Legalism-in-Eden-(Ferguson-Interview2c-pt-4).aspx)