George Whitefield (1771). “The Works of the Reverend George Whitefield ...: Containing All His Sermons and Tracts which Have Been Already Published ; with a Select Collection of Letters Written to His Most Intimate Friends, and Persons of Distinction, in England, Scotland, Ireland, and America, from the Year 1734, to 1770 ; Including the Whole Period of His Ministry ; Also, Some Other Pieces on Important Subjects, Never Before Printed”, p.173