Another psalm, a song for the dedication of the house, by David. This is what the scripture says (Psalm 149:5): "Let the faithful exult in glory, let them sing for joy on their couches." When the righteous depart from this world, three companies of angels attend them: one says (Isaiah 57:2) "Peace be upon him," another says, "Let them sing for joy on their couches," and a third says, "He is going in peace, and his going is in the hands of the Lord."
Rabbi Yehuda bar Simon said in the name of Rabbi Yoshiya: It is as if the Holy One, blessed be He, says to the departed, "Peace be upon you." From whom did you learn this about the wicked? As it is said (Isaiah 57:21), "There is no peace, says the Lord, for the wicked." If God said this to the wicked, all the more reason for Him to say "peace" to the righteous.
Therefore, "Let the faithful exult in glory." What is the glory that the Holy One, blessed be He, bestows upon the righteous when they depart this world and praise Him? Rabbi Chiya bar Yosei said: There is no difference between the living righteous and the dead except for speech alone, and they praise the Holy One, blessed be He, saying that He has placed them in the bundle of life, as it is said (1 Samuel 25:29), "But the soul of my lord shall be bound up in the bundle of life."
"Let them sing for joy on their couches." "Sing for joy" means nothing other than dancing, as it is said (Psalms 118:15) a voice of singing and salvation in the tents of the righteous." Rabbi Yochanan said: "When an elder sits and teaches and his lips move and murmur in the grave, it is said (Song of Songs 7:10) 'Your palate is like the best wine.' And it is written (ibid. 7:9) 'Your lips drip honey.'
Therefore, let us rejoice in their beds. David said (Psalms 23:6) 'Surely goodness and mercy shall follow me all the days of my life, and I will dwell in the house of the Lord forever.' Did David think that he would live forever? Rather, Rabbi Yehuda said that this should be said in synagogues and study halls.
The Holy One, blessed be He, said to him, 'Even though you are dead, your name does not depart from My house forever. Rather, with every sacrifice that is brought, they mention you and recite songs of yours, such as a Psalm of David.' Moreover, the Holy One, blessed be He, said, 'Since you intended to build the Temple, even though your son Solomon built it in your name, I will call it by your name and write it as a song of David, as it is said, "A Psalm, a Song for the Dedication of the House, of David" (Psalms 30:1). Only for David and not for Solomon is it said.'"...