The Scripture moreover testifies that believers in this life have to struggle with various carnal doubts, and that under grievous temptations they do not always feel this full assurance of faith and certainty of persevering. But God, who is the Father of all consolation, does not suffer them to be tempted above that they are able, but will with the temptation make also the way of escape, that they may be able to endure it (1 Cor. 10:13), and by the Holy Spirit again inspires them with the comfortable assurance of persevering.
This certainty of perseverance, however, is so far from exciting in believers a spirit of pride, or of rendering them carnally secure, that on the contrary it is the real source of humility, filial reverence, true piety, patience in every tribulation, fervent prayers, constancy in suffering and in confessing the truth, and of solid rejoicing in God; so that the consideration of this benefit should serve as an incentive to the serious and constant practice of gratitude and good works, as appears from the testimonies of Scripture and the examples of the saints.
Neither does renewed confidence of persevering produce licentiousness or a disregard of piety in those who are recovered from backsliding; but it renders them much more careful and solicitous to continue in the ways of the Lord, which He has ordained, that they who walk therein may keep the assurance of persevering; lest, on account of their abuse of His fatherly kindness, God should turn away His gracious countenance from them (to behold which is to the godly dearer than life, and the withdrawal of which is more bitter than death) and they in consequence thereof should fall into more grievous torments of conscience.
And as it has pleased God, by the preaching of the gospel, to begin this work of grace in us, so He preserves, continues, and perfects it by the hearing and reading of His Word, by meditation thereon, and by the exhortations, threatenings, and promises thereof, and by the use of the sacraments.
The carnal mind is unable to comprehend this doctrine of the perseverance of the saints and the certainty thereof, which God has most abundantly revealed in His Word, for the glory of His Name and the consolation of pious souls, and which He impresses upon the hearts of the believers. Satan abhors it, the world ridicules it, the ignorant and hypocritical abuse it, and the heretics oppose it. But the bride of Christ has always most tenderly loved and constantly defended it as an inestimable treasure; and God, against whom neither counsel nor strength can prevail, will dispose her so to continue to the end. Now to this one God, Father, Son, and Holy Spirit, be honor and glory forever. Amen.