וַיַּגְרֵ֤ס בֶּֽחָצָץ֙ שִׁנָּ֔י הִכְפִּישַׁ֖נִי בָּאֵֽפֶר׃
און ער האָט צעבראָכן מיט שטײנדלעך מײַנע צײן, ער האָט מיך געװעלגערט אין אַש.
Shulchan Arukh, Orach Chayim
6. One who is able should only eat burnt bread in salt and a flask of water in the Parting Meal. Rema: There are those that are strict after eating the bread to dip into ash and to eat on the word(s) "And he has broken in gravel..." (Lamentations 3:15)