Rambam - Sefer HaMitzvos: Positive Mitzvah 240: Positive Mitzvah 240

Positive Mitzvah 240: Damage Caused by Grazing Animals
Exodus 22:4 "If a man shall cause his livestock to eat in a field..."

Mimi's family has a goat in the backyard of their home.

Her baby brother is allergic to other milk and fresh goat's milk was the only solution. There is an empty lot between Mimi's house and the neighbors. Often, the goat is allowed to graze on the weeds that grow in the lot.

One day, Mimi was holding on to the goat's leash loosely as she watched a bicycle race going on down the block.

"Mimi!" she suddenly heard her mother call from the kitchen window.

"Look at the goat! Its leaning over into our neighbor's garden. He just planted radishes last week. Quick, pull the goat back!"

Mimi's mother was lucky she noticed the goat before it nibbled at her neighbor's vegetable garden. She would have been responsible for any damage the goat had caused. This Positive Mitzvah deals with laws applying to damage caused by grazing.

Some people think that if they did something beautiful yesterday, or last week, or even several years ago, they've done their part and G-d should continue paying them for it the rest of their life. It's something like loaning money -- you lend it to someone last year and you're still making a profit off him today.
Problem is, the Torah prohibits charging interest -- even from G-d. If you did good yesterday, do twice as good today.

From: Bringing Heaven Down to Earth by Tzvi Freeman - tzvif@aol.com