Luther's disappearance during his return to Wittenberg was planned.
Frederick III had him intercepted on his way home in the forest near Wittenberg by masked horsemen impersonating highway robbers.
They escorted Luther to the security of the Wartburg Castle at Eisenach.
During his stay at Wartburg, which he referred to as "my Patmos", Luther translated the New Testament from Greek into German and poured out doctrinal and polemical writings.
These included a renewed attack on Archbishop Albrecht of Mainz, whom he shamed into halting the sale of indulgences in his episcopates, and a "Refutation of the Argument of Latomus," in which he expounded the principle of justification to Jacobus Latomus, an orthodox theologian from Louvain.

In this work, one of his most emphatic statements on faith, he argued that every good work designed to attract God's favor is a sin.
All humans are sinners by nature, he explained, and God's grace (which cannot be earned) alone can make them just.
On 1 August 1521, Luther wrote to Melanchthon on the same theme: "Be a sinner, and let your sins be strong, but let your trust in Christ be stronger, and rejoice in Christ who is the victor over sin, death, and the world.
We will commit sins while we are here, for this life is not a place where justice resides."

In the summer of 1521, Luther widened his target from individual pieties like indulgences and pilgrimages to doctrines at the heart of Church practice.
In On the Abrogation of the Private Mass, he condemned as idolatry the idea that the mass is a sacrifice, asserting instead that it is a gift, to be received with thanksgiving by the whole congregation.
His essay On Confession, Whether the Pope has the Power to Require It rejected compulsory confession and encouraged private confession and absolution, since "every Christian is a confessor."
In November, Luther wrote The Judgement of Martin Luther on Monastic Vows.
He assured monks and nuns that they could break their vows without sin, because vows were an illegitimate and vain attempt to win salvation.

In 1521 Luther dealt largely with prophecy, in which he broadened the foundations of the Reformation, placing them on prophetic faith.
His main interest was centered on the prophecy of the Little Horn in Daniel 8:9–12, 23–25.
The antichrist of 2 Thessalonians 2 was identified as the power of the Papacy.
So too was the Little Horn of Daniel 7, coming up among the divisions of Rome, explicitly applied.

Luther made his pronouncements from Wartburg in the context of rapid developments at Wittenberg, of which he was kept fully informed.
Andreas Karlstadt, supported by the ex-Augustinian Gabriel Zwilling, embarked on a radical programme of reform there in June 1521, exceeding anything envisaged by Luther.
The reforms provoked disturbances, including a revolt by the Augustinian friars against their prior, the smashing of statues and images in churches, and denunciations of the magistracy.
After secretly visiting Wittenberg in early December 1521, Luther wrote A Sincere Admonition by Martin Luther to All Christians to Guard Against Insurrection and Rebellion.
Wittenberg became even more volatile after Christmas when a band of visionary zealots, the so-called Zwickau prophets, arrived, preaching revolutionary doctrines such as the equality of man, adult baptism, and Christ's imminent return.
When the town council asked Luther to return, he decided it was his duty to act.
Luther's disappearance during his return to Wittenberg was planned. Frederick III had him intercepted on his way home in the forest near Wittenberg by masked horsemen impersonating highway robbers. They escorted Luther to the security of the Wartburg Castle at Eisenach. During his stay at Wartburg, which he referred to as "my Patmos", Luther translated the New Testament from Greek into German and poured out doctrinal and polemical writings. These included a renewed attack on Archbishop Albrecht of Mainz, whom he shamed into halting the sale of indulgences in his episcopates, and a "Refutation of the Argument of Latomus," in which he expounded the principle of justification to Jacobus Latomus, an orthodox theologian from Louvain.
In this work, one of his most emphatic statements on faith, he argued that every good work designed to attract God's favor is a sin. All humans are sinners by nature, he explained, and God's grace (which cannot be earned) alone can make them just. On 1 August 1521, Luther wrote to Melanchthon on the same theme: "Be a sinner, and let your sins be strong, but let your trust in Christ be stronger, and rejoice in Christ who is the victor over sin, death, and the world. We will commit sins while we are here, for this life is not a place where justice resides."
In the summer of 1521, Luther widened his target from individual pieties like indulgences and pilgrimages to doctrines at the heart of Church practice. In On the Abrogation of the Private Mass, he condemned as idolatry the idea that the mass is a sacrifice, asserting instead that it is a gift, to be received with thanksgiving by the whole congregation. His essay On Confession, Whether the Pope has the Power to Require It rejected compulsory confession and encouraged private confession and absolution, since "every Christian is a confessor." In November, Luther wrote The Judgement of Martin Luther on Monastic Vows. He assured monks and nuns that they could break their vows without sin, because vows were an illegitimate and vain attempt to win salvation.
In 1521 Luther dealt largely with prophecy, in which he broadened the foundations of the Reformation, placing them on prophetic faith. His main interest was centered on the prophecy of the Little Horn in Daniel 8:9–12, 23–25. The antichrist of 2 Thessalonians 2 was identified as the power of the Papacy. So too was the Little Horn of Daniel 7, coming up among the divisions of Rome, explicitly applied.
Luther made his pronouncements from Wartburg in the context of rapid developments at Wittenberg, of which he was kept fully informed. Andreas Karlstadt, supported by the ex-Augustinian Gabriel Zwilling, embarked on a radical programme of reform there in June 1521, exceeding anything envisaged by Luther. The reforms provoked disturbances, including a revolt by the Augustinian friars against their prior, the smashing of statues and images in churches, and denunciations of the magistracy. After secretly visiting Wittenberg in early December 1521, Luther wrote A Sincere Admonition by Martin Luther to All Christians to Guard Against Insurrection and Rebellion. Wittenberg became even more volatile after Christmas when a band of visionary zealots, the so-called Zwickau prophets, arrived, preaching revolutionary doctrines such as the equality of man, adult baptism, and Christ's imminent return. When the town council asked Luther to return, he decided it was his duty to act.
Martin Luther