2. Question: Why if fruit just ripened as Shabbos came in one cannot eat them even after Shabbos until maaser was taken but if he was eating a cluster of grapes for example and Shabbos came in and he put them down to eat after Shabbos then you can finish eating them after Shabbos and you don’t need to take maaser from them?
a. Fruits are only obligated in tithing once they are set or designated for a personal use for example if they are brought into the house to be eaten (which excludes selling them) not if they are being noshed on in the field.
b. These cluster of grapes were originally being eaten in the field and did not need to be tithed at the time. But if he would want to continue to eat them on Shabbos then he would have to tithe them (though he can’t on Shabbos) but since he put them down for after Shabbos then when he continues to eat them after Shabbos he is exempt from taking maaser as long as he has not brought them into his house yet.
c. On Shabbos fruit become set because the verse says “and you shall call the Shabbos a delight” where we learn from the verse that we have a mitzvah to eat delicacies on Shabbos. (See Shulchan Aruch Yoreh Deah 331:111, 114 and Shach 127, 130)
Answer: If you would be eating the fruit on Shabbos then you are designating it for a certain purpose, namely the mitzvah of delighting in Shabbos that set it and makes it obligated in tithing even if it is not brought into the house but if you put down the cluster of grapes as Shabbos comes in showing that you are done eating and you don’t want to eat it on Shabbos then Shabbos can’t set it for tithing because you have no intention of eating it on Shabbos and it is still just in the field to nosh on.