Samuel Bolton, in his book The True Bounds of Christian Freedom, lays out nine differences between legal obedience and evangelical obedience.  He writes:

1.  Slavish spirit vs. Childlike spirit

“In one case the man does things in a legal spirit, either hoping to get rewards by it, or fearing punishments if he omits the duty.  The godly man, on the other hand, goes about duty for the sake of obtaining communion with God, and knows it to be his reward and happiness to have that communion, while the lack of it is the greatest punishment he can endure.”

2.  Burdensome vs. Delight

“To the man who has to do with nothing but duty while he is performing duty, to him duty is tedious; but to those who have to do with God, with Christ, in their duties, to them duty is a delight. . . . The godly man has to do with God.  He labours, he breathes, his heart gapes for him.  He it is who he has in his eyes, and whom he labours after in prayer, even if he cannot enjoy Him.”

3.  Conviction of conscience vs. Necessity of nature

“With many, obedience is their precept, not their principle; holiness their law, not their nature.  many have convictions who are not converted; many are convinced they ought to do this and that, for example, that they ought to pray, but they have not got the heart which desires and lays hold of the things they have convictions of, and know they ought to do.  Conviction, without conversion, is a tyrant rather than a king; it constrains, but does not persuade; it forces, but does not move and incline the soul to obedience.  It terrifies but does not reform; it puts a man in fear of sin and makes him fear the omission of duty, but it does not enable him either to hate sin or love duty.  All that it does is out of conviction of conscience, not from the necessary act of a new nature. Conscience tells a man that he ought to do certain things, but gives him no strength to do them.  It can show him the right way and tell him what he ought to do, but it does not enable the soul to do it.  Like a milestone by the roadside, it shows the traveler the way, but does not give him strength to walk in the way.  On the other hand, where there is the principle of the Gospel, where there is grace, it is in the soul as a pilot in a ship who not only points the way but steers the vessel in the way which he appoints.”

4.  Satisfaction in duty vs. Satisfaction in Christ

“The one kind of man looks for his satisfaction in the duty by the performance of the duty, the other looks for satisfaction in the duty as he finds Christ thereby; it is not in the duty, but above the duty, that he finds his satisfaction.”

5.  Shell vs. Substance

“The one kind of man contents himself with the shell, the other is not content without the substance.  The godly man goes to duty as the means of communion with God; the other goes to duty merely to satisfy the grumblings and quarrels of his conscience.”

6.  Performance as self-righteousness vs. Performance as Christ’s righteousness

“The one type of man performs duty in order to live but it. . . . But the believer prays and performs duty, yet he looks beyond them, and looks to live by Christ alone. . . . Even though he has done both these things in abundance, yet for his acceptance he looks up to Christ as if he himself had done nothing at all.”

7.  Formality vs. Fervency

“The one man does things coldly and formally, the other fervently. . .  A natural man may pray earnestly at times when in fear or horror, under pangs of conscience, but he does not cry believingly.  There may be much affection in a prayer when there is but little faith; there may be fleshly affections, natural affections, affections heightened either from convictions or fears or horrors.  Yet these are but the cries of nature, of sense, and of reason, the cries of flesh, not of faith.  Affections based on true faith are not loud, yet they are strong; they may be still, yet they are deep; though they are not so violent, yet they are more sweet, more lasting.”

8.  Duty only when pressured vs. Duty continually with happiness

“The formal man does duty with a view to it serving other ends, and especially when he finds himself in extreme difficulties. . . . But it is not so with the godly man.  He closes with these duties as his heaven, as a part of his happiness, a piece of his glory.  He does not close with them from a necessity of submission, but out of delight; these things are not his penance but his glory and his desire.”

9.  Duty with reluctance vs. Duty with delight

“The one man engages in duty as it if were medicine, not food.  He is reluctant to perform it; he has no pleasure in it; he is driven to it only because he conceives that his soul’s health demands it.  But the godly man engages in duty as a healthful man sits down to meat; there is delight, desire, and pleasure in he exercise.”

– Samuel Bolton, The True Bounds of Christian Freedom, 140-44.