He began to do this in 1527 in the Libellus visitatorius, which urges pastors to instruct their people in the necessity of repentance, and to bring the threatenings of the law to bear upon men in order to faith.
Among his works, which were first collectively published in 1867-1876, are Absolutissimus de octo orationis partium constructione libellus (Antwerp, 1530), Rudimenta Grammatices (London, 1539), Daily Devotions, Monition to a Godly Life, Epistolae ad Erasmum, and commentaries on different parts of the Bible.
An abridgment of the latter part of it, the little Libellus Islandorum (to which the title of the bigger Liber - Islendingabok- is often given), was made by the historian for his friends Bishops Ketil and Thorlak, for whom he wrote the Liber (c. 1137).
He also wrote a suggestion for reform in the administration of justice entitled Libellus de optimo ordine forenses lites audiendi et deferendi; an Apologia, written to answer the charges brought against him by Louis XI.; a Breviloquium, or allegorical account of his own misfortunes; a Peregrinatio; a defence of Joan of Arc entitled Opinio et consilium super processu et condemnatione Johanne, dicte Puelle, and other miscellaneous writings.
This narrative, as written out by Adamnan, was presented to Aldfrith the Wise, last of the great Northumbrian kings, at York about 701, and came to the knowledge of Bede, who inserted a brief summary of the same in his Ecclesiastical History of the English Nation, and also drew up a separate and longer digest which obtained great popularity throughout the middle ages as a standard guide-book (the so-called Libellus de locis sanctis) to the Holy Places of Syria.
His work The Book of Icelanders is unfortunately lost, but an abridgment of it, Libellus Islandorum, made by Ari himself, contains a significant reference to Vinland.
Besides an edition of the book of Job, .containing the original text, the Vulgate, and a new translation, he published a Latin version of the Moreh Nevochim of Maimonides (Director dubitantium ant per plexorum, 1520), and also edited in Latin the Aureus libellus of Aeneas Platonicus, and the Timaeus of Chalcidius.
After the first Diet of Spires (1526), where a precarious peace was patched up for the reformed faith, Melanchthon was deputed as one of twenty-eight commissioners to visit the reformed states and regulate the constitution of churches, he having just published a famous treatise called the Libellus visitatorius, a directory for the use of the commissioners.
In 1542 a tract, written by him and entitled Della Pienezza, suficienza, et satisfazione della passione di Christo, or Libellus de morte Christi, was made by the Inquisition the basis of a charge of heresy, from which, however, he successfully defended himself.