50] This article also affords a glorious testimony that the Church of God will exist and abide in opposition to all the gates of hell, and likewise teaches which is the true Church of God, lest we be offended by the great authority [and majestic appearance] of the false Church, Rom. 9:24. 25.
51] From this article also powerful admonitions and warnings are derived, as Luke 7:30: They rejected the counsel of God against themselves. Luke 14:24: I say unto you that none of those men which were bidden shall taste of my supper. Also Matt. 20:16: Many be called, but few chosen. Also Luke 8:8. 18: He that hath ears to hear, let him hear, and: Take heed how ye hear. Thus the doctrine concerning this article can be employed profitably, comfortingly, and savingly [and can be transferred in many ways to our use].
52] But a distinction must be observed with especial care between that which is expressly revealed concerning it in God's Word, and what is not revealed. For, in addition to what has been revealed in Christ concerning this, of which we have hitherto spoken, God has still kept secret and concealed much concerning this mystery, and reserved it for His wisdom and knowledge alone, which we should not investigate, nor should we indulge our thoughts in this matter, nor draw conclusions, nor inquire curiously, but should adhere [entirely] to the revealed Word [of God]. This admonition is most urgently needed.
53] For our curiosity has always much more pleasure in concerning itself with these matters [with investigating those things which are hidden and abstruse] than with what God has revealed to us concerning this in His Word, because we cannot harmonize it, which, moreover, we have not been commanded to do [since certain things occur in this mystery so intricate and involved that we are not able by the penetration of our natural ability to harmonize them; but this has not been demanded of us by God].
54] Thus there is no doubt that God most exactly and certainly foresaw before the time of the world, and still knows, which of those that are called will believe or will not believe; also which of the converted will persevere [in faith] and which will not persevere; which will return after a fall [into grievous sins], and which will fall into obduracy [will perish in their sins]. So, too, the number, how many there are of these on either side, is beyond all doubt perfectly known to God. 55] However, since God has reserved this mystery for His wisdom, and has revealed nothing to us concerning it in His Word, much less commanded us to investigate it with our thoughts, but has earnestly discouraged us therefrom, Rom. 11:33ff , we should not reason in our thoughts, draw conclusions, nor inquire curiously into these matters, but should adhere to His revealed Word, to which He points us.
70] Therefore, whoever would be saved should not trouble or harass himself with thoughts concerning the secret counsel of God, as to whether he also is elected and ordained to eternal life, with which miserable Satan usually attacks and annoys godly hearts. But they should hear Christ [and look upon Him as the Book of Life in which is written the eternal election], who is the Book of Life and of God's eternal election of all of God's children to eternal life: He testifies to all men without distinction that it is God's will that all men should come to Him who labor and are heavy laden with sin, in order that He may give them rest and save them, Matt. 11:28.
71] According to this doctrine of His they should abstain from their sins, repent, believe His promise, and entirely trust in Him; and since we cannot do this by ourselves, of our own powers, the Holy Ghost desires to work these things, namely, repentance and faith, in us through the Word and Sacraments. 72] And in order that we may attain this, persevere in it, and remain steadfast, we should implore God for His grace, which He has promised us in Holy Baptism, and, no doubt, He will impart it to us according to His promise, as He has said, Luke 11:11ff : If a son shall ask bread of any of you that is a father, will he give him a stone? Or if he ask a fish, will he for a fish give him a serpent? Or if he shall ask an egg, will he offer him a scorpion? If ye, then, being evil, know how to give good gifts unto your children, how much more shall your heavenly Father give the Holy Spirit to them that ask Him!
-Solid Declaration of the Formula of Concord XI 50-54, 70-72