148. My eyes have prevented the night watchers. (21) The Psalmist here intimates, that he was more sedulously intent on meditating upon the law of God than watchmen of the night were to keep watch. Others are of opinion, that the verb שוח, suach, is put for to discourse. If this opinion is admitted, the sense will be, that the Prophet, not from ostentation, but for the welfare of his brethren, was so desirous of communicating instruction, that he gave himself no rest. The word meditate is, however, more appropriate in this place; for the night is an unseasonable time for discoursing upon the law of God; but at that season, when alone, he silently recalled to his memory what he had previously learned, so that he passed no part of the night without meditating upon the law.
(21) The Hebrews divided the natural day into three portions--morning, noon, and evening — which are mentioned by David as seasons in which he engaged in prayer. (Psalms 55:17.) They also divided the night into three parts, called “watches,” consisting of four hours each, and commencing at our six o’clock in the evening. In Lamentations 2:19, we read of the first watch; or, as it is there designated, “the beginning of the watches;” in Jude 7:19, of “the middle watch;” and in Exodus 14:24, of “the morning watch.” A similar division of the night seems to have been made by other ancient nations, as appears from the references made to it by Homer and the early Greek writers. The Greeks and Romans, however, in improving their military discipline, afterwards divided the night into four watches, each consisting of three hours; and when the Jews fell under the dominion of the latter people, they adopted from them this division of the night. Hence we read of “the fourth watch of the night” in Matthew 14:25. And the four watches are mentioned together in Mark 13:35 :
“Watch ye therefore: for ye know not when the master of the house cometh, at even, or at midnight, or at cock-crowing, or in the morning.”
The time at which each of these four watches began and ended is thus determined by Dr. Hales, who has written elaborately on the subject: “1. Οψε, the late, began at sunset, and ended with the third hour of the night, including the evening-dawn, or twilight. It was also called οψια ὡρα, eventide, Mark 11:11; or simply οψια, evening, John 20:19, etc. 2. Μεσονυκτιον, the midnight, lasted from the third hour till midnight. 3. Αλεκτοροφωνια, the cock-crowing, midnight till the third hour after, or the ninth hour of the night. It included the two cock-crowings, with the second or principal of which it ended. 4. Πρωι, the early, lasted from the ninth to the twelfth hor of the night, or sunrise, including the morning-dawn or twilight. It is also called πρωια, morning, or morningtide, ( ὡρα being understood,) John 18:28, etc.
“When the Psalmist here declares, that his eyes prevented the nightwatches, we are to understand him as chiefly referring to the middle and morning watches, which falling at that period of the night when men in general are devoted to rest, envinced the strength, fervour, and self-sacrificing character of his devotions.” — Dr. Morison.