The Jewish tradition of leaving stones or pebbles on a grave is an ancient one, and its origins are unclear. It is a custom or tradition, rather than a commandment, and over time many interpretations have been offered for this practice.
The following are several explanations:
1. During the times of the Temple in Jerusalem, Jewish priests (Kohanim) became ritually impure if they came within four feet of a corpse. As a result, Jews began marking graves with piles of rocks in order to indicate to passing Kohanim that they should stay back.
2. The Talmud mentions that after a person dies, the soul continues to dwell for a while in the grave where the person was buried. Putting stones on a grave keeps the soul ‘down’ in this world, which some people find comforting. Another related interpretation suggests that the stones keep demons from getting into the graves.
3. Flowers, though beautiful, will eventually die. A stone will not die, and symbolizes the permanence of memory and legacy.
Another traditional interpretation: The Hebrew word for ‘pebble’ is tz’ror – and it happens that this Hebrew word also means ‘bond.’ When we pray the memorial El Maleh Rahamim prayer (and at other times) we ask that the deceased be ‘bound up in the bond of life’ – tz’ror hachayim. By placing the stone, we show that we have been there, and that the individual’s memory continues to live on in and through us.
Many people take special care in choosing a stone to put on the grave of a loved one. It may be a stone from a place that was significant to the deceased, a stone that was chosen at an event during which the deceased was especially missed, or simply an interesting or attractive rock. Because there is no commandment to fulfill here, placing a stone on a grave is an opportunity for you to create your own ritual, or do things in a way that feels most meaningful to you.