When Ezra said, “The joy of the Lord is your strength” (Nehemiah 8:10)he was speaking to the remnant of Israel who has returned to Judah to rebuild the city and its temple. It was a time of restoration, not only of the ruined city, but also of obedience to the law of God.
There was sorrow and weeping when the people heard God’s law and realized how far they had gone away from its teaching. But Ezra told them to rejoice and celebrate because of the restoration (Nehemiah 8:9-12).. That’s when Ezra said, “The joy of the Lord is your strength”.
One discovery the elders made, as they returned to the scriptures, was that the feast of tabernacles had not been observed since the days of Joshua! (Nehemiah 8:13-17).
That was back before the destruction of Israel and Judah, before the great kingdom of David and Solomon, back even before the Judges. Within a generation of entering the promised land, God’s people had forgotten the annual feast of tabernacles.
Now in Ezra’s time, a time when Israel was but a stump, and life was very hard, the people went out to the mountains and gathered branches. They made the leafy booths on every housetop and in the city squares. They dwelled in tabernacles seven days as an observance of the covenant.
God’s law was now being obeyed again after such a long lapse. This caused God and the people to be glad and rejoice. The restoration gave joy to the Lord, and his joy was the strength of the people.
In the same way, when a remnant of God’s church goes back to the gospel covenant mediated by Christ, and they see the departures from it, and restore their obedience to it, then God is glad and the joy of the Lord is their strength.