The city shall be devoted, even it and all that is therein, to Yahweh: only Rahab the prostitute shall live, she and all who are with her in the house, because she hid the messengers that we sent.
Some Christians in recent years have taken to "prayer walking" in which they pray as they walk around a town asking God to save the residents. While modeled after the battle of Jericho, there are some significant differences. The Israelites marched around Jericho in response to a God-given directive to do so. Christians have no such command. In fact, we have been told to do something quite different: to proclaim the gospel to every creature as well as to pray for their salvation. God called the Israelites to announce bad news and to destroy Jericho, but He has called us to announce good news and to seek and save the lost. Whereas there is nothing wrong with walking around a town and praying for it, when this costs thousands of dollars, in some cases, and evangelism is not done, one wonders about the prudence of such an undertaking. Certainly we can and should pray for the lost, but there is no indication in Scripture that geographical proximity renders prayers more effective, though it may aid concentration in prayer. It might be better to stay home and pray, if we do not evangelize, and to spend our money equipping someone else to evangelize. Better still, go and do both: pray and evangelize.