The dedication of the wall is a day of dedication and celebration. It came after much hard work and was not free from problems in the process. God has been faithful. He called them back home and got them through the construction process. If they can keep their focus on God, then He will keep these walls strong. Nobody can tear down the walls except for Israel by turning their back on God. If they stand strong in their faith and unwavering in their commitment to God, no army can come against these walls and prevail. The issue with dedication is that they were dedicating the walls of Jerusalem, but the key test will be their personal dedication to the LORD.
Think about a church. We can have a dedication service to dedicate and celebrate the building of the church. But the true test of the church is not the dedication of the building. It is not the dedication of the people when they are in the building for worship services. It is the dedication and devotion of the people because we don't just go to church, but we are the church. We cannot forget that what we do outside of the church building will have a huge impact on the church and will impact our service unto the LORD. Sometimes churches seem to fall apart not because their worship services were lacking, but rather because the people's private lives were.