Why do Jews place coins on a gravestone?

Answer 1

Wrong. We place a pebble, not coins.

1. The Midrash Lekach Tov (Pesikta Zutra 35:20) relates that each of Jacob's sons took a stone and put it on Rachel's grave to make up Rachel's tomb. From this we learn that by placing stones on the grave one participates in building up the tombstone. In those days one did not mark a grave with marble or granite and a fancy inscription, but one made a cairn of stones over it. Each mourner coming and adding a stone was effectively taking part in the Mitzvah of matzevah ("setting a marker") as well as a symbolic levayat ha-meyt ("accompanying the dead"). Our present practice seems to be commemorative of this ancient tradition.

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2. The book Ta'amey Ha-Minhagim (The Reasons for the Customs, pp. 470-471) says, "We put pebbles on the grave to show that the visitor was at the grave. It was a sort of calling-card for the honor of the deceased, to mark that you have paid a visit." (See also Orach Haim 224:8).

A contemporary respondent, Rabbi Ovadia Yosef, confirms this custom, noting Eliyahu Rabba 224:7 as his source (Responsa Yabia Omer IV, Yoreh Deah 35).