MLA
Wesley, Charles, 1707-1788. Letter from Charles Wesley to "My dear Sally" [Sarah] Wesley, [Bristol] - July 7, 1776. July 7, 1776. Wesleyana Collection. Pitts Theology Library. https://digital.library.emory.edu/purl/941zcrjf0d-cor.
APA, 6th edition
Wesley, Charles, 1707-1788. (July 7, 1776)[Letter from Charles Wesley to "My dear Sally" [Sarah] Wesley, [Bristol] - July 7, 1776]. Wesleyana Collection, Pitts Theology Library. https://digital.library.emory.edu/purl/941zcrjf0d-cor.
Chicago
Wesley, Charles, 1707-1788, Letter from Charles Wesley to "My dear Sally" [Sarah] Wesley, [Bristol] - July 7, 1776, July 7, 1776, Wesleyana Collection, Pitts Theology Library. https://digital.library.emory.edu/purl/941zcrjf0d-cor.