What does Isaiah 25:9 mean?
Some commentators interpret this as people erupting in praise for the Lord. They would be responding to the removal of death and the end of the reproach of sin (Isaiah 25:7–8). Isaiah declares that these words will be used on that day.Together, God's people declare that He is their God. Their relationship with Him has been characterized by waiting for Him. People who trust in the Lord wait for Him to keep His promises. All that waiting has now proven to have been worthwhile. Their faith in what they could not see is proven in this moment. They wait for the Lord to save them once and for all, and now He has done it just as He said He would. The Lord always comes through in His promises.
The people call to each other to be glad and to rejoice in His salvation of them. What other response could there possibly be to this news?