Fausset's Bible Dictionary
Watches of the Night
The Jews reckoned three military watches: the "first" or beginning of the watches (Lamentations 2:19), from sunset to ten o'clock; the second or "middle watch" was from ten until two o'clock (Judges 7:19); the third, "the morning watch," from two to sunrise (Exodus 14:24; 1 Samuel 11:11). Afterward under the Romans they had four watches (Matthew 14:25): Luke 12:38, "even, midnight, cockcrowing, and morning" (Mark 13:35); ending respectively at 9 p.m., midnight, 3 a.m., and 6 a.m. (compare Acts 12:4.) Watchmen patrolled the streets (Song of Solomon 3:3; Song of Solomon 5:7; Psalms 127:1).
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Fausset, Andrew R. Entry for 'Watches of the Night'. Fausset's Bible Dictionary. https://www.studylight.org/dictionaries/eng/fbd/w/watches-of-the-night.html. 1949.