From A Concise History of Romania (Cambridge Concise Histories), by Keith Hitchins (Cambridge, 2014), Kindle Loc. 680-700, 728-740:
The attachment of the Romanians to the East is perhaps most visible in the persistence of Slavic or, more precisely, Middle Bulgarian as the language they mainly used for serious writing and other purposes well into the first half of the seventeenth century. The adoption by the Romanians of Slavic as their liturgical language and the language of the princely chancelleries in the fourteenth century was an event of singular importance in their development. Slavic reinforced their ties to the Byzantine cultural and religious world and served as the primary instrument for the transmission of its sacred and secular heritage. The Romanians could accept Slavic as the language of the church because it ranked with Greek, Hebrew, and Latin, and they used it in the affairs of state precisely because of its prestige as a sacred language. But Slavic could not become their religious language in the full sense of the term. Spoken by a part of the clergy, the great boiers, and scholars, it was never the language of the mass of the population, who said their prayers and created a rich folk literature in Romanian.
Monasteries were the major centers of cultural activity in the principalities. Besides spiritual and educational functions, monks were preoccupied between the fifteenth and the first half of the seventeenth century with the copying of Slavic manuscripts, of which some 1,000 have survived. These copyists were thus responsible for preserving the Middle Bulgarian and, to some extent, the Slavo-Serbian versions of the greater part of the Byzantine–Slav religious literary patrimony. Princes were among the most ardent patrons of manuscript copying and embellishment. Ştefan cel Mare was always keenly aware as an Orthodox sovereign of his religious responsibilities to his own people and to the peoples of the Balkans under Ottoman rule and of his role as God’s representative on earth, and thus he was a prodigious builder of churches and monasteries and richly endowed them in Moldavia and throughout the Orthodox East with beautiful manuscripts for church services. Although the value of these manuscripts today is scholarly rather than as pieces of original literature, they reveal much about the intellectual and spiritual needs of the upper strata of Romanian society. The manuscripts were mainly religious in content, but their readers were not limited to monks and priests. It is evident from notations on the manuscripts that boiers, chancellery clerks, and the middle class also looked to them for spiritual guidance. The ascetic, mystical view of life was thus not confined to the monastery, but encompassed significant elements of the literate secular society.
Among the relatively few original compositions in Slavic or Slavo-Romanian, as it is often called because of influences of Romanian, were the earliest works of Romanian historiography.
The Protestant Reformation, though it gained few religious converts, deeply affected cultural life and the sense of identity in the principalities and among the Romanians of Transylvania. It offered further evidence that the Romanian medieval worldview was far from being impervious to influences from the West.
The absence of texts in Romanian before the sixteenth century may be attributed to the belief among the literate classes that the spoken language was not as suitable for sacred writings, legal documents, and history as Slavic. It is significant that the oldest text in Romanian that has survived is a private letter about practical matters written by a merchant in Câmpulung, in Wallachia, to the magistrate of Braşov, in Transylvania, warning of the movement of Ottoman troops. It is dated 1521, the same year that Neagoe Basarab completed his “Advice” in Slavic. The differences in the Romanian of the letter from modern Romanian are slight, and the style is polished, evidence that the language had been used in writing for some time in correspondence and even in rough drafts of official documents before their translation into Slavic.
Romanian was introduced as the written language in secular affairs in the second half of the sixteenth century, as the princely chancelleries ceased using Slavic exclusively, Moldavia in 1574 and Wallachia in 1593. The first chronicle in Romanian, an original work, not a translation, dealt with the reign of Mihai Viteazul and was composed in Wallachia about 1597. This and the so-called “Moldavian Chronicle,” now lost, composed several decades later, laid the foundations for the flowering of historiography in Romanian beginning in the middle decades of the seventeenth century.