In 1620 Fra Obicini's travelled to Jerusalem to the Emir of Beirut, Fakhr ad-Din II. The background to this mission began seven years earlier, in 1613, when Fakhr ad-Din II had taken refuge in Tuscany, Italy. The emir formed an alliance with the Medici ruler, Cosimo II, and spent two years under his protection. He spent three more in Sicily and Naples seeking, and failing, to rally a Crusade against Ottoman rule. By 1618 the changed political situation permitted his return to Lebanon. Two years later Friar Obicini journeyed to Jerusalem in an embassy with Lord Battista Tarquet, the Consul of all Palestine, sent by the consul of Sidon, the Christian King, Lord Albert Gardana and the Prosecutor of the Holy Land, Lord Francis Lebar. In Beirut, Obicini was, according to his account, warmly and lavishly received by the emir ad-Din, who had readily granted the two Christian holy sites, the Grotto of the Annunciation, i.e. the Grotto of Nazareth, and Mount Tabor to his Franciscan order. In his description of the acquisition of the holy sites he recounts how he travelling to Nazareth, as a small group of a priest, friar John of Vendôme, and a Sicilian friar, Francesco Salice, had brought letters from the Princes, various testimonials, and a decree from the Qadi of Safed. On Saturday 29 November 1620, the group took possession of the sanctuary built on the foundations of the House of Loreto and known as the Holy Grotto - the site venerated by Christians as the place where the Angel Gabrielannounced the birth of Christ to the Virgin Mary. While Obicini was abbot in the convent of Aleppo, Syria he had mastered Syriac, Arabic, Hebrew, Aramaic, and Coptic languages. In 1621, he was the first lector in Arabic in the San Pietro in Montorio convent and was a precursor of Athanasius Kircher. In 1631 Obicini published Grammatica Arabica; a Latin translation of the 13th-14th century Arabic grammar Al-Ājurrūmīyya,, by Abū Abdullaahi Muhammad bin Muhammad bin Dāwūd aṣ-Ṣanhaajī, known as Ibn Adjurrum. In 1636 Obicini published Thesaurus Arabico-Syro-Latinus, his opus magnum; a Latin expanded translation of Elijah of Nisibis's 11th-century glossary intended to assist Latin-speaking prelates in converting Syrians and other Arabic speakers.
Literature
Thesaurus Arabico-Syro-Latinus by Thomas Obicinus; , 1636. .
Mufadhdhal ibn 'Umar Al Abharí Īsāghūkhī, Isagoge. Id est, breve Introductorium Arabicum in Scientiam Logices : cum versione latina: ac theses Sanctae Fidei. R. P. F. Thomae Novariensis ... opera studioque editae... Quae quidem publice disputabuntur... Objectis satisfaciente P. F. P. Marietta, etc., Thomas Obicini, 1625
Obicini, Thomas, Grammatica Arabica. Agrumia appellata. Cum versione Latina, ac dilucida expositione. Rome, Congregatio de Propag. Fide, 1631
Van Lantschoot, Arnold, Un précurseur d'Athanase Kircher : Thomas Obicini et la Scala Vat. copte 71, Louvain : Muséon, 1948 - XV, 87 p,