Psalm 98:8-9 Let the floods clap their hands: let the hills be joyful together [9] Before the Lord ; for he cometh to judge the earth: with righteousness shall he judge the world, and the people with equity.
The *floods* that are encouraged to clap and the *hills* that are told to rejoice, are both analogous of the ungodly. The reason they are told to clap and rejoice? Verse 9 lay it out, God was coming to judge the earth with righteousness and equity. And here we see again how scripture testifies of the Messiah!
Jesus said that he came into this world *for Judgment* (John 9:39), he also said that his *judgment is just* (equity).
Jesus brought God's righteous judgment into this world, but why would God encourage the ungodly to rejoice at this? Shouldn't they be afraid of it?
Because the righteous judgment of God is not unto condemnation i.e. its purpose isnt to condemn us, but rather its purpose is to bring victory (Jesus) to us:
Matthew 12:20 A bruised reed shall he not break, and smoking flax shall he not quench, *till he send forth judgment unto victory*.
John 3:17 For God sent not his Son into the world to condemn the world; but that the world through him might be saved.
The righteous judgment bring salvation within reach of all mankind. This is why God encourages the floods and the hills to clap and rejoice. For Christ has come and they (the ungodly) can be redeemed through repentance and faith in him, for those who reject this... they are condemned already. Selah!