Donate to Yeshiva:[1] The Chabad custom is to donate during the meal, or after the meal, a sum of money to a Yeshiva as a pre-payment towards tuition for one’s child in that Yeshiva.

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[1] Hayom Yom p. 41; Sefer Haminhagim p. 23; Toras Menachem 2:281; Igros Kodesh 30:300;  Kovetz Minhagei Chabad Inyanei Hirayon Vileida p. 33; Shevach Habris 19:5