Jonathan Edwards teaches the doctrine of perseverance in this passage, which is about as far removed from the easy believism most understand when they say “once saved always saved” as you can get.
” . . .as soon as ever a soul has put forth one act of faith towards Jesus, it becomes interested in his righteousness, and so in all the benefits that are purchased by it. The soul is thenceforward united to Christ, and Christ is his and all that he has. When a soul has believed in Christ, God stands bound to do all the rest for him. He stands bound to bestow grace to persevere in faith and holiness, and to carry on his work, even to eternal life.
When once any person has by faith committed himself into the hands of Christ, Christ has promised that he will keep them, and that they never shall pluck them out of his hands. John 10:28, “My sheep shall never perish, neither shall any pluck them out of my hands.” But,
of a title to salvation. There never is a title to salvation without it. Though it han’t the righteousness by which a title to life is attained, yet none have that righteousness that don’t persevere; and that because although it is not proper to say that perseverance is necessary in order to justification, yet a persevering principle is necessary in order to justification. In order to a title to Christ’s righteousness, ’tis necessary that there should be such a qualification in the heart; that is as it were a seed of perseverance, and such a foundation that perseverance will be the certain result of it ‘Tis necessary that there should be “such an heart in them” in order to justification (Deuteronomy 5:29). ‘Tis necessary that a man should believe in Christ, and cleave to Christ in a persevering way: a temporary faith don’t justify. But in order to that, persons must have that faith that is of a persevering, everlasting sort. He must have that sort of seed that is an abiding seed. ‘Tis not a vanishing but a durable faith that justifies. Though perseverance be not an act performed, till after persons have finished their days; yet perseverance is looked upon as virtually performed in the first act of faith, because that first act is of such a nature as shows the principle to be of a persevering sort.
Perseverance is necessary to salvation, as ’tis the necessary consequence and evidence of effectual calling. ‘Tis an evidence that universally attends uprightness, and the defect of it, an infallible evidence of want of uprightness. Jonathan Edwards , Sermons and Discourses, 1734–1738 (WJE Online Vol. 19) , Ed. M. X. Lesser, page 600-601