I used to believe firmly in Eternal Security but it is refuted by the Bible constantly.
Take the Gospel of Luke for Example:
[11] Now the parable is this: The seed is the word of God.
[12] The ones along the path are those who have heard; then the devil comes and takes away the word from their hearts, that they may not believe and be saved.
[13] And the ones on the rock are those who, when they hear the word, receive it with joy; but these have no root, they believe for a while and in time of temptation fall away.
[14] And as for what fell among the thorns, they are those who hear, but as they go on their way they are choked by the cares and riches and pleasures of life, and their fruit does not mature.
[15] And as for that in the good soil, they are those who, hearing the word, hold it fast in an honest and good heart, and bring forth fruit with patience. (Luke 8:11-13)
[42] And the Lord said, "Who then is the faithful and wise steward, whom his master will set over his household, to give them their portion of food at the proper time?
[43] Blessed is that servant whom his master when he comes will find so doing.
[44] Truly, I say to you, he will set him over all his possessions.
[45] But if that servant says to himself, `My master is delayed in coming,’ and begins to beat the menservants and the maidservants, and to eat and drink and get drunk,
[46] the master of that servant will come on a day when he does not expect him and at an hour he does not know, and will punish him, and put him with the unfaithful. (Luke 12:42-46)
Church Fathers:
“Watch for your life’s sake…for the whole time of your faith will not profit you, if ye be not made perfect in the last time.” Didache, 16 (A.D. 90).
“And as many of them, he added, as have repented, shall have their dwelling in the tower. And those of them who have been slower in repenting shall dwell within the walls. And as many as do not repent at all, but abide in their deeds, shall utterly perish…Yet they also, being naturally good, on hearing my commandments, purified themselves, and soon repented. Their dwelling, accordingly, was in the tower. But if any one relapse into strife, he will be east out of the tower, and will lose his life.” Hermas, The Shephard, 3:8:7 (A.D. 155).
“[T]hat eternal fire has been prepared for him as he apostatized from God of his own free-will, and likewise for all who unrepentant continue in the apostasy, he now blasphemes, by means of such men, the Lord who brings judgment [upon him] as being already condemned, and imputes the guilt of his apostasy to his Maker, not to his own voluntary disposition.” Justin Martyr,(A.D. 156).
“Now, in the beginning the spirit was a constant companion of the soul, but the spirit forsook it because it was not willing to follow. Yet, retaining as it were a spark of its power…But the Spirit of God is not with all, but, taking up its abode with those who live justly, and intimately combining with the soul, by prophecies it announced hidden things to other souls.” Tatian the Syrian, To the Greeks, 13 (A.D. 175).
“Christ shall not die again in behalf of those who now commit sin, for death shall no more have dominion over Him; but the Son shall come in the glory of the Father, requiring from His stewards and dispensers the money which He had entrusted to them, with usury; and from those to whom He had given most shall He demand most. We ought not, therefore, as that presbyter remarks, to be puffed up, nor be severe upon those of old time, but ought ourselves to fear, lest perchance, after [we have come to] the knowledge of Christ, if we do things displeasing to God, we obtain no further forgiveness of sins, but be shut out from His kingdom. And therefore it was that Paul said, ‘For if [God] spared not the natural branches, [take heed] lest He also spare not thee, who, when thou wert a wild olive tree, wert grafted into the fatness of the olive tree, and wert made a partaker of its fatness.’” Irenaeus, Against Heresies, 4:27:2 (A.D. 180).
“But some think as if God were under a necessity of bestowing even on the unworthy, what He has engaged (to give); and they turn His liberality into slavery. But if it is of necessity that God grants us the symbol of death, then He does so unwilling. But who permits a gift to be permanently retained which he has granted unwillingly? For do not many afterward fall out of (grace)? Is not this gift taken away from many?” Tertullian, On Repentance, 6 (A.D. 204).
“Confession is the beginning of glory, not the full desert of the crown; nor does it perfect our praise, but it initiates our dignity; and since it is written, ‘He that endureth to the end, the same shall be saved,’ whatever has been before the end is a step by which we ascend to the summit of salvation, not a terminus wherein the full result of the ascent is already gained.” Cyprian, Unity of the Church, 21 (A.D. 251).
