Jamieson, Fausset and Brown on Isaiah 25:9

9. And it shall be said in that day, &c.--"After death has been swallowed up for ever, the people of God, who had been delivered from the hand of death, shall say to the Lord, Lo, this is our God, whom unbelievers regarded as only a man" [Jerome]. "The words are so moulded as to point us specially to the person of the Son of God, who 'saves' us; as He vouchsafed to Israel temporal saving, so to His elect He appears for the purpose of conferring eternal salvation" [Vitringa]. The Jews, however, have a special share in the words, This is our God (see on Is 25:6).

we have waited--"Waited" is characteristic of God's people in all ages (Ge 49:18; Tit 2:13).

we will be glad and rejoice in his salvation--compare Psa 118:24, which refers to the second coming of Jesus (compare Psa 118:26, with Lu 13:35).