Midrash sa Sofonias 3:14: Pesikta Rabbati & Midrash Tehillim

Zephaniah also came and said: "Stand and accept your cup of comfort." She said: What do you have in your cup? He said: "Cry out in gladness, O Daughter Zion! Shout joyfully, O Israel! Be glad and exult with all your heart, O daughter Jerusalem! The Lord has annulled your judgment, He has turned away your enemy; The King of Israel, the Lord, is in your midst, you have no further fear of misfortune. On that day, [God] will say to Jerusalem: Take courage, Zion! Let not your hands fall slack. The Lord your God is in your midst, a warrior who brings victory. He will rejoice over you with gladness, He will be silent in His love, He will delight in you with shouts of joy" (Zephaniah 3:14-20).

Let us rejoice to God. This is what the verse says (Zephaniah 3:14): "Sing, daughter of Zion; shout aloud, O Israel! Be glad and rejoice with all your heart, Daughter Jerusalem!" On what matter (Micah 7:9) has your enemy been deprived of his right to rule? All rejoice at the downfall of the wicked. And similarly, it says (Isaiah 14:5-6): "The Lord has broken the rod of the wicked, the scepter of the rulers, which in anger struck down peoples with unceasing blows, and in fury subdued nations with relentless aggression." What is written (ibid. 14:7)? "All the lands are at rest and at peace; they break into singing." And it says (Ezekiel 32:31): "All the earth's kings lie in state, each in his own tomb. But you are cast out of your tomb like a rejected branch; you are covered with the slain, with those pierced by the sword, those who descend to the stones of the pit. Like a corpse trampled underfoot." When is the earth joyful? When I make you desolate. And similarly, it says (Psalms 149:6): "Let the high praises of God be in their mouths and a double-edged sword in their hands." And it says (Proverbs 11:10): "When the wicked perish, there is rejoicing." Let us approach Him with thanksgiving, let us sing psalms to Him, great is the power of gratitude. And similarly, Jonah says (Jonah 2:10): "And I, with a song of thanksgiving, will sacrifice to You."

Another thing, for it is good to sing praises to our God. As Isaiah said (Isaiah 52:7), "How beautiful upon the mountains, etc." When the Lord reigns, all announce the good news, as it is said (ibid.), "Bringing good news and proclaiming peace." And it is said (Zephaniah 3:14), "Sing aloud, O daughter of Zion, etc." About what? "The Lord has taken away the judgments against you." So when the Lord reigns, all praise Him. And thus it says above this passage, "The Lord will reign forever." The King of the universe is worthy of praise for His Kingdom. At that moment, all sing, all praise, all exalt when they see Him as King. Therefore it is said (Isaiah 52:7), "Tell Zion, 'Your God reigns!'" And what is written after that? "Your watchmen lift up their voices, etc." And it is said (Zephaniah 3:14), "Sing aloud, O daughter of Zion, etc." About what? "The Lord has taken away the judgments against you." So when the Lord reigns, they sing praises to Him. Therefore it is said, "For it is good to sing praises to our God." A human king, even if he is great and has the power to strike, if a poor man asks for his peace, it is a disgrace to him and he does not answer him. But the Lord is not like that. Everything is acceptable to Him and He says, "Praise Me, for it is good before Me." As it is said, "For it is good to sing praises to our God, etc." "Who builds Jerusalem, etc." Just as the Lord is King in praise and songs, so Jerusalem is not built except in praise and songs. And you find this in the last building, which Hiram built. As it says (Ezra 3:10-11), "They laid the foundation of the temple and they sang responsively in praising and giving thanks, etc." Therefore it is said, "For it is good to sing praises to our God."