Quietness is Sustained by God's Commands

[The grace of inward quietness] is sustained by faith in God’s commands; that is to say, by a belief, that they are true, that they are reasonable, that they ought to be obeyed, and that they cannot be disobeyed without danger. 

The man of true faith and strong faith feels, that the command, FRET NOT THYSELF, and others like them are as binding upon us, as any other commands which are admitted to be of the most solemn and imperative nature. Immense is the error and the evil, which has arisen from man’s attempting to make distinctions, where they ought not to be made. The sin of an unquiet or fretful spirit is not the same, it is true, with other sins; but the obligation, which attends the command not to indulge in such a sin, is the same. No man can knowingly violate such an obligation, although it relates to a matter which the world is very apt to designate as of small consequence, without showing that his heart is not right with God. 

Wherever God’s command is, no matter how small the thing is to which the command relates, obedience must follow. Otherwise sin lies at the door. The man of faith, deeply realizing this, feels himself bound by that sacred and paramount obligation which God’s command always carries with it, to guard against the least impatience, the least unquietness of spirit. Bound by the command, supported by the promise, with his heart filled with love, and added to all this, meeting God as it were face to face in his providences, he understands the import of those delightful expressions; “They, that trust in the Lord, shall be as mount Zion, which cannot be removed, but abideth forever. As the mountains are round about Jerusalem, so the Lord is round about his people from henceforth, even forever.” Psalm 125:1, 2.

— from The Life of Faith, Part 2, Chapter 13

Quietness is Sustained by God's Promises

The grace of quietness of spirit is sustained by faith in God’s promises. The man of true faith is very far from considering the afflictions of God’s people the same thing with their being cast off and rejected. On the contrary, relying on God’s promises, he has not a doubt, that their trial will in due season be changed into redemption, and their mourning into victory. Abraham had his long day of trial; but his hopes deferred were ultimately satisfied and made rich in the gift of Isaac, “the son of promise.” The patriarch Joseph endured the severe trial of his faith in exile and imprisonments and in false accusations; but at length, in the language of the author of the Mute Christian, “he changed his iron fetters into chains of gold, his rags into royal robes, his stocks into a chariot, his prison into a palace.” David also was afflicted in his youth; but was victorious in age. He, who dwelt in caverns and made his pillow upon a rock, was at last seated upon the throne of Israel. Once the humble keeper of his father’s sheep, and known only in the solitudes of his native vallies, he became, in God’s time, the shepherd and ruler of a mighty people; great in his renown, great in his achievements, and greater still in being able to bear testimony to the favor and faithfulness of God. The man of faith understands this. He knows it all. It is written in letters uneffaceable on the centre of his heart. And is it strange, therefore, marking as he does the bow of promise in the dark cloud that overhangs him, that he should be resigned and quiet in spirit? “The steps of a good man,” says the Psalmist, “are ordered by the Lord; and he delighteth in his way. Though he fall, he shall not be utterly cast down, for the Lord upholdeth him with his hand.”

— from The Life of Faith, Part 2, Chapter 13.