 Frederick III, Elector of Saxony had him discreetly intercepted on his way home by masked horsemen and escorted to the security of the Wartburg Castle at Eisenach, where Luther grew a beard and lived incognito for nearly eleven months, pretending to be a knight called "Junker Jörg".During his stay at Wartburg (May 1521-March 1522), which he referred to as "my Patmos", Luther translated the New Testament from Greek into German, and poured out doctrinal and polemical writings, including in October 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, a philosopher from Louvain.In a letter to Melanchthon of 1 August 1521, he wrote