I couldn't figure out how to attach this as a source but below is a link to William and Martha's marriage information. There isn't an image available but it is listed in the Georgia marriage records
https://www.familysearch.org/ark:/61903/1:1:Q2QK-68MP
"Georgia, County Marriages, 1785-1950," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:Q2QK-68MP : 7 February 2020), William A Guest and Martha A Brown, 23 May 1872; citing Marriage, Banks, Georgia, United States, Georgia Department of Archives and History, Morrow, FHL microfilm 1,597,743.