Adam Clarke on Nehemiah 4:9

We made our prayer unto our God, and set a watch - The strongest confidence in the protection and favor of God does not preclude the use of all or any of the means of self-preservation and defense which his providence has put in our power. While God works in us to will and to do, we should proceed to willing, through the power he has given us to will; and we should proceed to action, through the power he has given us to act. We cannot will, but through God's power; we cannot act, but through God's strength. The power, and the use of it, are two distinct things. We may have the power to will, and not will; and we may have the power to do, and not act: therefore, says the apostle, seeing God has wrought in you these powers, see that You Work Out Your Own salvation, with fear and trembling.