Moed Katan, Chapter Two, Mishnah Three
There are certain labors that are permitted on the festival because if they are not done immediately, the product will be ruined. However, this is only permitted if he did not purposely set his schedule so that the work would end up needing to be done during the festival.
1) A man may bring his produce indoors for fear of thieves and withdraw his flax from a soaking pool to prevent it spoiling, as long as he doesnt intend to do this work during the festival.
2) And all those who deliberately intended to do their work on the festival, they must leave it to spoil.
Section one: If one has left produce outside but fears that it might be stolen by thieves, he may bring it indoors on the festival. He may also take his flax out of a soaking pool (used to soften the flax so that it can be made into linen) lest it become too soft and spoil. However, he may not start a certain labor before the festival knowing that he will have to continue to do the work during the festival. The only time these labors may be performed is if some unforeseen circumstance prevented him from being able to perform them before the festival.
Section two: This is a summary of the basic rule governing all of the previous sections. If one has intentionally left over work for the festival, he must let it spoil. A different explanation is that this refers to a court which penalizes a person who left his work for the festival by taking it away from him. According to this interpretation we would need to translate the last clause as they cause him to lose [his property], which is a viable translation.