Joshua 22:5 But take diligent heed to do the commandment and the law, which Moses the servant of the Lord charged you, to walk in all his ways, and to keep his commandments, and cleave unto him, and to serve him with all your heart and with your soul.
The tribes of Reuben, Gad, and half Manasseh were given land east of Jordan, but they went to fight with the other tribes for the land in the West. When the Conquest was over, Joshua sent them back across Jordan to their land with these words of exhortation: be faithful to the Lord!
This verse is a summary of the response all believers make to the Lord for His blessing and mercy: take diligent heed to do the commandments God gave through Moses. Listen carefully and determine to do it. We do this when we hear the Law and are convicted of sin, and we hear the Gospel which gives the power and will to do.
We walk in all his ways. Walk means live regularly and naturally all the time. It means developing good habits that live God’s way without having to consciously plan every move. Moral uprightness is the natural, yea supernatural, reaction to receiving Grace.
We keep his commandments by believing in Christ, who forgives sin and graces us with God’s righteousness. They asked Jesus, “How do we do the works of God?” Jesus said, “Believe in Me.”
We cleave unto the Lord. Like a man cleaves to his wife in such a way that the two become one flesh. This is a mystery, like Christ and the Church. We don’t really a cleaving that makes us one. Unity is seldom seen and hard to grasp, but the Oneness of God and me is still a truth that is believed We who believe in Christ are in God.
We respond to the gospel by serving God. We serve Him by trusting, thanking, and worshiping. However, as Luther says, God does need our service, but other people do. We serve God by loving and serving others. A life of service is our faithful response to God’s love for us, which is shown at the cross. The bottom line: we love because He first loved us.