Although there are many restrictions on agricultural work on Hol HaMoed, work that is done for the needs of the holiday is permitted. For example, a person is allowed to water his field so that vegetables will grow and be ready to be eaten on the holiday, but if they are ready for harvest and are being watered to make them better, they cannot be watered. Rashi explains the latter case to be that they are being watered so that they will grow more and fetch a better price at the market after the holiday. Others forbid even watering them so that they will look nicer, which is not essential for eating them on Yom Tov.
To illustrate this story, the Gemara tells of Ravina and Rabba Tosefa’a who were walking together on Hol HaMoed and saw someone who was watering his vegetable garden. Rabba Tosefa’a called on Ravina to place the person under a ban for performing a forbidden activity on Hol HaMoed. Ravina responded that the person was undoubtedly watering them so that they will be eaten on the holiday, which the baraita teaches is permitted. Although Rabba Tosefa’a wanted to interpret the baraita differently, Ravina insisted that this was the correct interpretation of the baraita, and his colleague conceded that it is permitted.
Rabba Tosefa’a was one of the last of the amora’im, and he participated in the editing of the Talmud. Although we find a number of his rulings in the Gemara, since he was one of the last of the amora’im, few of his teachings remain. As we see evident in the above story, he was a student of Ravina; after the passing of Mar bar Rav Ashi, he headed the academy in Sura for a period of six years. Some suggest that his nickname “Tosefa’a” stems from his encyclopedic knowledge of the Tosefta, while others think that it is the name of the city that was his home. Another likely possibility connects it with his word in adding material and editing the final version of the Gemara. Rav Sherira Ga’on records that he passed away in the year 474 CE.