Now the leaders of the people lived in Jerusalem, but the rest of the people cast lots to bring one out of ten to live in Jerusalem, the holy city, while nine-tenths remained in the other cities. (Nehemiah 11:1
Now that the walls and gates of Jerusalem were restored, it was necessary to get the Jews to populate the holy city. It would be difficult to protect the city without people to guard the walls and gates. Why rebuild the city if you don't plan to live there? In other words, God needed people -- live bodies -- to inhabit the city.
I like what Warren Wiersbe says about this in his commentary "Be Determined." He says, "Never underestimate the importance of simply being physically present in the place where God wants you. You may not be asked to perform some dramatic ministry, but simply being there is a ministry." (p. 144)
The very presence of the Jewish people in Jerusalem acted as a witness to the skeptical Gentiles around them who constantly posed a threat to their security. Seeing men patrolling the walls and gates provided a deterent to attack.
God places you and me in different places to act as his sentinels to shout the alarm when sinister forces try to overcome his beloved people. We are his sirens to warn against the attacks of the evil one. We need to take our task seriously and be on alert all the time for opportunities to stand in the gap against evil forces. How do we do this? Through the power given us in the Word of God and the indwelling Holy Spirit. What did Jesus use when he was tempted by the devil? He said, "It is written." The Word is our sword so let's use it mightily for the Lord.