today's other readings are Rev. 15: 1-4 and Lk. 21: 12-19
A word of explanation about this reflection - it is much more a teaching than a reflection for one to ponder. But that's okay, as every once in a while, it is good to learn more about the Word of God. For such knowledge can help us to appreciate it more.
The Book of Psalms, or Psalter, is a collection of religious songs, most of which are thought to be composed in the 5th and 4th century B.C. They truly were songs meant to be sung, sometimes by one person, and sometimes by groups of people. Some were composed to be used in the Temple in Jerusalem, while the rest could be sung elsewhere, such as a local synagogue.
The most common type of psalm is supplication to God for His help in various spiritual and temporal needs. But there are many of thanksgiving and praise to God, while there are a few that are meant to consider a problem or teach a lesson.
Psalm 98 is a psalm of thanksgiving to God, in which God is extolled for the victory he has given to Israel (verses 1-3); which is then followed by the thought that all the nations of the earth and all of creation should welcome the just Saviour with joy. According to Jewish teaching, Psalm 98 is the tenth and last song the Jewish people will sing after the final redemption.
This psalm, you will notice, forms the basis of the hymn that is sung in verses 3-4 of today's first reading, in which they sing the song of Moses, the servant of God, and the song of the Lamb, Jesus Christ.