The snip of the marriage record is:
"Nathan [Gates] and Abigail Knowlton, June 17, 1790"
The source citation for this record is:
Systematic History Fund, Vital Records of Westminster, Massachusetts, to the End of the Year 1849 (Worcester, Mass.: F.P. Rice, 1908), Marriages, page 142: Nathan Gates and Abigail Knowlton entry.
3) The Westminster town record of the marriage: