“…we set a watch against them day and night…” – Nehemoah 4:9

Nehemiah says, “we set a watch against them day and night.” What! Is there to be someone sitting up all night? Of course there is. If Sanballat had told them when he meant to attack them, they might have gone to sleep at other times; but as he did not give them that information, they had to set a watch “day and night.” The devil will not give you notice when he is going to tempt you; he likes to take men by surprise; therefore, set a watch day and night.

It was a work quickened by knowledge. they knew that Sanballat would come if he could, so they set a watch. The more you know of the plague of your own heart, the more you will set a watch against it. The more you know of the temptations that are in the world through lust, the more you should set a watch. The older you are, the more you should watch. “Oh!” says an aged friend, “you should not say that; it is the young people who go wrong.” Is it? In the Old Testament or in the New, have you an instance of a young believer who went astray? The Bible tells us of many old men who were tripped up by Satan when they were not watching; so you have need to set a watch even when your hair turns grey, for you will not be out of gunshot of the devil until you have passed through the gate of pearl into the golden streets of the New Jerusalem. ~ C.H. Spurgeon

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