[Obedience to God’s will would], they say, be a burden too heavy for Christians! As if we could think of anything more difficult than to love God with all our heart, all our soul, and all our strength! Compared with this law, everything ought to be considered easy—whether the requirement to love our enemy or to banish all desire for revenge from our hearts. All these are indeed hard and difficult for our feebleness, even to the least detail of the law [cf. Matt. 5:18; Luke 16:17]. It is the Lord in whom we act virtuously. … To be Christians under the law of grace does not mean to wander unbridled outside the law, but to be engrafted in Christ, by whose grace we are free of the curse of the law, and by whose Spirit we have the law engraved upon our hearts [Jer. 31:33].

—John Calvin
Institutes, 2.8.57.