Cyclopedia of Biblical, Theological and Ecclesiastical Literature
is a Wesleyan custom. Near the beginning of Methodism the members of that body in Bristol began to meet at night, that they might worship without interruption. Mr. Wesley, knowing that such meetings would-soon be misinterpreted, made them public, and for a time held them once a month. Afterwards, however, they were observed only on the eve of the new year, which custom prevails to a certain extent to the present time.
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McClintock, John. Strong, James. Entry for 'Watch-Night'. Cyclopedia of Biblical, Theological and Ecclesiastical Literature. https://www.studylight.org/encyclopedias/eng/tce/w/watch-night.html. Harper & Brothers. New York. 1870.