Quotes by Martin Luther on Eternal Security
It matters not a whit that this King is despised. I will nonetheless treasure him like a precious jewel, for the Scripture states, "Blessed are they whosoever shall not be offended in me," and "whoever endures to the end shall be saved." If we reject him now, we are left with as little excuse as the Jews. So, let us not say, If our prince accepts the gospel, then we will too. (The Complete Sermons of Martin Luther, vol. V, p. 36)
If you are a Christian, you should read Decoding Nicea. Read why here.
[The Lord] cautions his Christians against becoming secure, so that the day of his coming might not come upon them unawares. … We must not become like those secure and ungodly people who crowd their hearts with surfeiting [excess] and concerns about earning a livelihood. … When they are at their securest … they will suddenly be laid low and burn with a fire that will never be extinguished. (The Complete Sermons of Martin Luther, vol. V, p. 38, brackets mine)
That's the way things will be, says Christ, when Judgment Day nears. The whole world will act secure. Don't let this disturb you. Christ admonishes, do not follow them; do not do what they are doing; cling to me. Nor be afraid; keep your head high, and see to it that, when I come down from heaven, I shall be able to find you! … But those who overload their hearts and show no concern for Judgment Day will find that death has suddenly overtaken them. The fellow who frolics and dances merrily with his wench, will then suddenly find himself flat on his face, and, while his next-door neighbor counts his shekels of silver and gold, he will suddenly be knocked down with his money bags and all. …
For this reason Christ says to his disciples and Christians, Be on your guard so that I do not find you in this rowdy crowd. When they say, Nothing to worry about, at that very moment they will be lying flat on their faces. (The Complete Sermons of Martin Luther, vol. V, p. 40-41)
God will avenge and severely punish the haughty rebellion of all who misuse the gospel, rich or poor. Would to God, that the punishment could be delayed for a while by our prayers! … Rebellion is so great and widespread that God will have to put a stop to it. No amount of warning or admonition, pleading or begging, no amount of threats or punishments by either spiritual or secular authority will do any good; God himself will have to step in with avenging judgment to punish and put an end to such wickedness. (Complete Sermons of Martin Luther, vol. VII, "Twenty-Second Sunday after Trinity," par. 31)
True, it is difficult to do good and in turn receive nothing but ingratitude. Remember, however, that you are a Christian, and if you wish to remain a Christian, you will have to exert yourself more earnestly than the non-Christian, as exemplified by our Father in heaven. That is a promise. If you in your heart forgive him who has offended you, so in turn you will be forgiven by God and men. (The Complete Sermons of Martin Luther, vol. VI, pp. 273-74)