In 1760 while in Constantinople he met with his brother according to the flesh Chrysanthos the Aitolos († 1785), from whom he learned the art of rhetoric. His missionary work in continental and insular Greece was ambitious, wondrous, successful and important.
He preached simply, ripely, heartfelt, expressively, humbly and gracefully. He spoke "according to my ability, not as a teacher, but as a brother; Christ alone is our teacher." "You are children and daughters of our Christ", he would say to his audience, "and not only am I not worthy to teach you, but even to kiss your feet, because each of you by your speech are more honorable than the whole world." Elsewhere he characteristically and humbly observed: "When I heard these sweet words, my brethren, that our Christ said, 'my heart was devoured for years as if by worms' for our Christian brethren, and I went out and walked from land to land and place to place to save their souls and teach my Christian brethren."
For his over two decades of rich work preaching he passed through Constantinople, Thrace, Macedonia, Thessaly, Central Greece, Peloponnesos, Epirus and the islands of the Aegean and Ionian seas. His fiery sermons were particularly successful in the hungry and tired souls of the enslaved, as his good disciple and biographer Sapfeiros Christodoulides says: "Wherever the thrice-blessed one went, there was a large gathering of Christians and they listened with compunction and reverence to the grace and sweetness of his words, and this was followed by a great correction and benefit to the soul." And St. Nikodemos the Hagiorite writes: "His teaching was, as we his listeners became, most simple, like that of the fishermen; it was serene and gentle, where it appeared to be entirely full of the grace of the cheerful and quiet Holy Spirit." He continues: "And God above cooperated and confirmed his words with the signs and miracles that followed, and through these miracles he confirmed the preaching of his sacred mission." In North Epirus "he cooperated with divine grace, and he produced many and great fruits, so that he tamed the wild, calmed the bandits, soothed the ruthless and unmerciful, showed mercy to the irreverent, made the illiterate to be reverent, taught those who were ignorant divine things, and he caused them to run to the Divine Services. And simply all sinners he brought to great repentance and correction, so that all said that in their time there appeared a new Apostle."
All his biographers especially emphasize that he suffered to establish schools that Greek children could learn letters for free, "that they may be established in the faith and in reverence, to be led towards a virtuous life and disposition." He also persuaded the rich to buy fonts for the churches that did not have them. In this way 400 fonts were purchased, as well as books for the illiterate and prayer ropes and crosses for all the faithful, around 500,000. He did not hesitate to stigmatize the trade of the Jews which they did on Sunday, and he did not allow Christians to work on the Day of the Lord. This is why the Jews mortally hated him.
On his journeys he was followed by many priests and many people. Every sermon in each place was a sacred rite. He would tell Christians to prepare, confess and fast. The priests performed the Mystery of the Sacred Unction, and they anointed the Christians. Everywhere a large wooden Cross was set up, they lit candles, and he stood on his stool, distributing blessings, bread, kollyva, and then he taught. The Cross would remain to commemorate his passage and often worked miracles. His disciples took notes, and this is how we have his teachings today, accompanied by the miracles and prophecies. His prophecies mention the liberation of the enslaved Nation, the future of various individuals, cities and mankind, the discoveries of science and other subjects. Many of these things took place with true precision.
Despite the great love of the people who were beneficiaries of the Saint, and the respect harbored for him even by the Turks, there were also certain people who hated him, such as certain wealthy kodjabashis, because he rebuked their various injustices, but especially the Jews, whom he also rebuked in his sermons. "Of course, the Saint did not suffer from anti-semitism. Rather here he was speaking words of truth. He knew that Jews were behind many of the injustices and persecutions of the Christians." He wrote in a letter to his brother Chrysanthos a few months before his death: "Ten thousand Christians love me and one hates me. A thousand Turks love me and one not so much. A thousand Jews want me dead and one does not."
The Jews slandered him to the Turkish authorities, and managed with a lot of money given to Ahmet Kurt Pasha of Berat to achieve his killing. The Saint foreknew his end and on his last night "he showed no signs of sadness for his withdrawal from this life, but he even appeared graceful in his face, as if he was going to joys and revelry." They hanged him from a tree in the village of Kolikondasi and threw his honorable relic in the Apsos River. Despite the fact that they tied a rock around his neck, his relic washed ashore. It was found by the pious priest Mark and buried in the Monastery of the Theotokos Ardenica. The Saint was martyred on August 24, 1779. In August of 1813 the translation of his honorable relic took place. The following year a church and monastery were built in his honor by command of Ali Pasha of Ioannina, which he had prophesied about.
Saint Kosmas the Aitolos was honored very early on as a Saint by the faithful people. Proof of this honor and love are the hundreds of icons, frescoes, engravings, woodcuts, drawings, shrines and churches. The canonical act of his recognition took place by the Ecumenical Patriarchate on April 20, 1961. In 1984 the authors P.B. Paschou and P.F. Christopoulos found the relics of the Saint in the ruins of his Monastery in Albania. There is a fairly rich bibliography concerning the Saint.
His Service and Life were composed by St. Nikodemos the Hagiorite, Sapfeiros Christodoulides (1814), Thomas Paschides (1860) and Monk Gerasimos Mikragiannanites. His Supplication Service was written by Metropolitan Seraphim of Arta.
His memory is celebrated on August 24th.
Source: From the book Synaxarion of Vatopaidi. Translated by John Sanidopoulos.