John Brown of Haddington was a poor, orphaned shepherd boy in 1742 or so when, having been affected following a series of illnesses by a spiritual awakening in connection with reading the Bible and various theological works (he mentions the Westminster Larger Catechism and the expositions of the Shorter Catechism by Thomas Vincent and John Flavel, Joseph Alleine's Alarm to the Unconverted, William Guthrie's The Christian's Great Interest, Samuel Rutherford's Letters, and Thomas Gouge's Christian directions Shewing How to Walk with God All the Day Long), Brown was inspired to take it upon himself to learn the Latin, Greek and Hebrew languages. It is said that, leaving his sheep "on the braes of Abernethy" in the care of a trusted companion, he set off on a midnight hike to St. Andrews, twenty-four miles away. The next morning he visited a bookseller seeking to purchase a Greek New Testament. The bookseller only smiled at his request, but a Professor from the University of St. Andrews, having engaged him in conversation, told him that if he could read a passage from the Testament, he would buy the book for him. He did so, and obtained the book, which was the beginning of a life-long love of languages that would lead him to learn Greek and Hebrew without a tutor, and Latin, studying under a tutor for one month; as well as, later, Arabic, Syrian, Persian, Ethiopian, French, Spanish, Dutch, German and Italian.
After mastering the first three languages, he casually conferred with a student at the University about his accomplishments, but this individual took it amiss and accused him of having acquired his great linguistic learning by means of a compact with the Devil. Others supported his accuser, and in fact, the accusation, as outrageous as it sounds, dogged him over the years to such an extent that at one point he was denied a certificate of church membership based on this allegation. He was forced to vindicate his learning in a letter dated August 6, 1745 (when he was 23 years old), in which he gives an account of his studies and relates his thought processes in some detail, a published extract of which maybe found here (pp. 29-33). Despite the false aspersion, Brown would go on to become one of Scotland's greatest and most famous and godly ministers of the eighteenth century.
His great-grandson Dr. John Brown would later quip, speaking of the Devil, "That astute personage would not have employed him on the Greek Testament."