Ah, well I would say the concept is there because the concept is Jewish. May His great Name grow exalted and sanctified (Amen.) in the world that He created as He willed. May He give reign to His kingship in your lifetimes and in your days, and in the lifetimes of the entire Family of Israel, swiftly and soon. Now respond: Amen. (Cong Amen. May His great Name be blessed forever and ever.) May His great Name be blessed forever and ever. Blessed, praised, glorified, exalted, extolled, mighty, upraised, and lauded be the Name of the Holy One, Blessed is He (Cong. Blessed is He) beyond any blessing and song, praise and consolation that are uttered in the world. Now respond: Amen. May there be abundant peace from Heaven, and life upon us and upon all Israel. Now respond: Amen. He Who makes peace in His heights, may He make peace, upon us and upon all Israel. Now respond: Amen.
The one holy catholic apostolic church has believed in purgation and prayers for the dead for almost two thousand years. The Jews have been doing so even longer, unto this day. When a Jew dies, Kaddish is said for up to eleven months to purify the deceased from such venial sins. In all of the Messiah's recorded conversations with Jews, or teaching, there is no mention of it to overturn this belief among the Jews.
A mourner says Kaddish to help along the soul of the deceased in its journey upwards.
Since there is no mention it means it was adopted by the NT church? In Mark 5:38-41 Christ dismissed the professional mourners.
So they’ve been wrong a long time.
Big deal.
They’re keeping pretty good company, as lots of people have been wrong about stuff for a long time.