[Psalms 98:1] O SING UNTO THE LORD A NEW SONG; FOR HE HATH DONE MARVELLOUS THINGS: HIS RIGHT HAND, AND HIS HOLY ARM, HATH GOTTEN HIM THE VICTORY.
Sforno (Obadiah ben Jacob Sforno, 1475-1550, Bologna, Italy): HE will avrenge HIS honor on the Day of Vengeance.
All they who persecuted and tormented Judah desecrated the honor of the Almighty. They will be punished.
[Psalms 98:2] THE LORD HATH MADE KNOWN HIS SALVATION: HIS RIGHTEOUSNESS HATH HE OPENLY SHEWED IN THE SIGHT OF THE HEATHEN.
Seforno: HATH MADE KNOWN. The Day of Redemption was sealed and unknown until God decided to reveal it by bringing it to come.
HIS RIGHTEOUSNESS. Seforno: Israel was exiled because of its sins and will be redeemed due to the kindness of the Almighty.
[Psalms 98:3] HE HATH REMEMBERED HIS MERCY AND HIS TRUTH TOWARD THE HOUSE OF ISRAEL: ALL THE ENDS OF THE EARTH HAVE SEEN THE SALVATION OF OUR GOD.
HIS MERCY. Hebrew "chasdoi" also connoting "kindness". The question here is whether the verse is referring to the "Mercy" of God or to that of Israel. Sforno quotes here the words God spoke to Israel, I REMEMBER THEE, THE KINDNESS OF THY YOUTH; WHEN THOU WENTEST AFTER ME IN THE WILDERNESS [Jeremiah 2:2].
ALL THE ENDS OF THE EARTH HAVE SEEN: Sforno says that the Future Redemption will happen in such a way that all the nations of the world will know that the Almighty has intervenes on behalf of Israel and they will be unable to ascribe their salvation to natural causes.
[Psalms 98:4] MAKE A JOYFUL NOISE UNTO THE LORD, ALL THE EARTH: MAKE A LOUD NOISE, AND REJOICE, AND SING PRAISE.
[Psalms 98:5] SING UNTO THE LORD WITH THE HARP; WITH THE HARP, AND THE VOICE OF A PSALM.
[Psalms 98:6] WITH TRUMPETS AND SOUND OF CORNET MAKE A JOYFUL NOISE BEFORE THE LORD, THE KING.
[Psalms 98:7] LET THE SEA ROAR, AND THE FULNESS THEREOF; THE WORLD, AND THEY THAT DWELL THEREIN.
All of Creation will be happy and rejoice to do the will of God. Nature itself will bear testimony to the Power of God and HIS intervention in the affairs of mankind.
[Psalms 98:8] LET THE FLOODS CLAP THEIR HANDS: LET THE HILLS BE JOYFUL TOGETHER
[Psalms 98:9] BEFORE THE LORD; FOR HE COMETH TO JUDGE THE EARTH: WITH RIGHTEOUSNESS SHALL HE JUDGE THE WORLD, AND THE PEOPLE WITH EQUITY.
Sforno: The righteous will not suffer because of the wicked.