(By Denis Greenan). Vatican City, July 1 - Pope Francis' eagerly awaited first encyclical will be published on Friday, less than four months after his election - the fastest in recent papal history. The work, Lumen Fidei or 'Light of the Faith', will build on a draft prepared by his predecessor Benedict XVI, who was unable to complete his own encyclical - which would have been his fourth - because of his shock resignation in February. Lumen Fidei will be presented by three senior clergy, Vatican spokesman Father Federico Lombardi said Monday. He said the Vatican will print 500,000 copies of the Italian edition of the initial print run. It will sell for 3.50 euros and will be 90 pages in small format, Lombardi said. Last month Francis spoke in his customary off-the-cuff way about how happy he was to take over where Benedict had left off with his "powerful" writing about spreading the faith. The Argentine pope said the encyclical would be co-written by his German predecessor - although the Vatican statement announcing the presentation did not mention Benedict. "Now an encyclical written by four hands is coming out," Francis said at a mid-June bishops' follow-up meeting after last October's synod about new evangelization. At the time Francis said the encyclical would likely take the place of a definitive post-synod statement, expanding on it. Benedict, who resigned at the end of February and is now pope emeritus, presided over that synod. Francis, the first Jesuit and Latin American pope, was elected March 13. "Pope Benedict started it and he delivered it to me. It's a powerful document," said Francis The Argentine pontiff thanked his German predecessor for his "great work", which he said he would "carry on". A post-synod "exhortation" would make no sense because it would be overshadowed and superseded by the encyclical, Francis said. The encyclical would sum up the findings of the synod and enlarge on it, talking about "evangelization in general". The synod on new evangelization ended on October 24 with a call to "the People of God," to more actively spread the Gospel message. The bishops agreed that this was "not a question of finding new strategies as if the Gospel was to be spread like a market product, but rediscovering the ways in which individuals come close to Jesus". Benedict was originally expected to complete the encyclical in the first half of 2013 but his resignation, announced to a stunned world on February 11 and carried out on February 28, made this impossible. It was to coincide with the Year of Faith currently underway. The encyclical was to have been Benedict's fourth, after the best-selling trilogy Deus Caritas Est (God Is Love), published in 2006, Spe Salvi (Saved in Hope), in 2007, and Caritas in Veritate (Charity in Truth), in 2009. It will not be known until Friday whether the encyclical will carry the names of both Francis and Benedict, and how the current pope has used the material left to him by his predecessor.