In the spring of 1829, Joseph Knight was in his late fifties and lived with his large family in Colesville, New York, a long day’s journey from Joseph’s home in Harmony, Pennsylvania. He routinely supplied Joseph with food, shoes, cash, and paper to see him through the translation process. During one of his visits, Father Knight was “very anxious to know his duty as to this work.” Joseph asked the Lord, who answered with the revelation in section 12.
It says many similar things as revelations to Joseph Smith Sr. and Oliver Cowdery given earlier or around the same time: A great and marvelous work is about to be made known to mankind. Like a sword that cuts both ways, the Lord’s words can bless and curse, save and damn. The figurative field is ready for harvest. Whoever desires to harvest should do so all day long, saving his soul in the process. God calls whoever will harvest. If Father Knight will ask, God will answer. Since he has asked, the Lord tells him to keep the commandments and work for Zion.
One of the great souls who made the restoration possible, Joseph Knight obeyed this revelation. He did all in his power to bring forth the Book of Mormon. He transported Joseph Smith in his wagon when Joseph went to Fayette to organize the church in April 1830 and in his sleigh when Joseph moved to Ohio early in 1831. He was “first to administer to my necessities while I was laboring in the commencement of bringing forth the work of the Lord, and of laying the foundation of the Church of Jesus Christ of Latter-day Saints,” Joseph remembered. “Faithful and true, and even handed, and exemplary and virtuous and kind.”
 “History, 1838–1856, volume A-1 [23 December 1805–30 August 1834],” p. 21, The Joseph Smith Papers, accessed September 22, 2020.
From Doctrine and Covenants Minute
Joseph Knight Sr. was an instrumental figure in the coming forth of the Book of Mormon. Father Knight first met Joseph Smith in 1826 when he hired him as a day laborer. The Knights lived in Colesville, New York, near the place where Joseph was working for Josiah Stoal. Around this time Joseph began his courtship of Emma Hale. Father Knight later recalled, “I furnished him with a horse and Cutter [sleigh] to go and see his girl down to Mr. [Hales]” (Dean Jessee, “Joseph Knight’s Recollection of Early Mormon History, BYU Studies, 17:1, 4). Joseph Knight Jr. recorded that “My father . . . hired many hands. In  he hired Joseph Smith. Joseph and I worked together and slept together. My father said that Joseph was the best hand he ever hired. We found him a boy of truth. He was about 21 years of age.” While staying with the Knights, Joseph grew close enough to them to share about his divine calling. “He made known to my father and I that he had seen a vision, that a personage had appeared to him and told him where there was a gold book of ancient date buried, and that if he would follow the direction of the angel, he could get it,” Knight Jr. later wrote. He continued: “We were told in secret. . . . My two older brothers did not believe in such things; my father and I believed what he told us, I think we were the first after his father’s family” (William G. Hartley, Stand By My Servant Joseph, 2003, 11).
After the loss of the initial Book of Mormon manuscript, Father Knight was an invaluable source of support and encouragement for Joseph. From January to May 1829, Knight visited Joseph several times, providing financial help to assist in the translation. Joseph Knight Jr. later recalled, “Father and I often went to see him [Joseph] and carry him something to live upon” (Knight, Autobiographical Sketch, 1). In May 1829 when Joseph and Oliver Cowdery were running low on supplies they temporarily halted translation and traveled to see Father Knight. Although he was not at home when they arrived, Knight heard they were in need of assistance and soon traveled to Harmony with paper and provisions to assist in the translation. It is likely during this visit that Joseph received the revelation in section 12 (Jessee, 10). This revelation first appeared in the 1833 Book of Commandments (Book of Commandments, 1833, p. 31, JSP).
See Historical Introduction, “Revelation, May 1829–B [D&C 12],” p. 31, The Joseph Smith Papers, accessed October 6, 2020, https://www.josephsmithpapers.org/paper-summary/revelation-may-1829-b-dc-12/1.