I have heard some people say in Yiddish after "Hamokom Yenachem Eschem B'Soch Shaar Aveilei Tzion V'Yerushalayim" ("May God comfort you alongside the mourners of Zion and Jerusalem"), "Zulst Mer Nisht Visen Fun Kein Tzaar," or in Hebrew "ולא יוסיפו לדאבה עוד" ("you should no more know of any sorrow"). What is the source of this add on saying in Yiddish or in Hebrew? Is it something that should be said?
This is the end of verse 31:11 from Yirmiyahu.
Rav Yehudah Aryeh Dunner of Bnei Brak in his שאלות המצויות - ח"ג עמ' קז quotes Rav Shmuel Vosner ZTL that the reason this phrase was added was because the words המקום ינחם אתכם are in future tense, and thus may sound like one is telling the avel (mourner) that he should be consoled in the future too. Therefore the minhag was to add this wish (in yiddish or Hebrew) stating that the avel should have no future pain or sorrow.