“We set a watch against them day and night, because of them.” – Nehemiah 4:9

“We set a watch.” Brethren, if we are to watch over ourselves, and we must do so, we must do it with a definite purpose. We must not say, “I must try to be watchful.” No, no; you must be watchful; and your watchfulness must be as distinct and definite an act as your prayer. “We set a watch.” Some of you have seen the guards changed in the barracks; there is a special time for each company to mount guard. When you go to bed at night, pray the Lord to guard you during the darkness. In the morning, set a watch when you go to your business. Set a watch when you go to the dinner-table; set a watch when you return home. Oh, how soon we may be betrayed into evil unless we set a watch!

It was a work carefully done; for Nehemiah says, “We set a watch against them day and night, because of them.” Those three last words would be better rendered, “over against them”; that is, wherever there was an enemy, there he set a watch. They are likely to come up this way. Very well, set a watch there. Perhaps they may shift about, and come up this way. Very well, set a watch there. Possibly they may come climbing over the wall in front here. “Well, set a watch there. “We set a watch over against them.” One brother has a very hot temper. Brother, set a watch there. Another is very morose at home, critical, picking holes in other people’s coats. Brother, set a watch there. One friend has a tendency to pride, another to unbelief. Set a watch wherever the foe is likely to come. “We made our prayer unto our God, and set a watch over against them.” ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/2254.cfm