Musar su Rut 2:14

Rabbi Menachem HaBavli suggests the following rationale for the prohibition to the farmer to retrace his steps in order to gather in a sheaf he had overlooked previously (24,19): It is the nature of the evil urge to try and stop a person from performing deeds of loving kindness. It is accepted in kabbalistic circles that blessing reposes especially in what is a left-over. We know this from Ruth 2,14: "She ate, felt sated, and had some left over." We have a similar verse in Kings II 4,44: "When they had eaten they had some left over, as the Lord had said." The eyes of the poor are trained on G–d; He is their only hope. As soon as the owner of the field forgot this sheaf it became the property of the poor. Even if the owner of the field retraces his steps and collects this sheaf before one of the poor has seen it he still is considered as having robbed the poor. This is why the Torah asks you to consider such a sheaf as irretrievably lost to you the moment you become aware that you forgot it. If you fail to do so, you yourself will become impoverished having to beg for a hand-out on the threshing grounds. Thus far Rabbi Menachem Habavli.

There is a comment by the Midrash Hagadol on the words וישמע ראובן, in 37,21 which illustrates that the brothers did not understand Joseph's true motives. We are told there that the objective of the Torah in telling us of the purity of Reuben's motive, though he dared not express it at the time, was to tell us how highly G–d rates the performance of a good deed when such deed is performed without ulterior motives. Had Reuben known that his deed would be recorded by the Torah and be read in public for millennia, he would have carried Joseph back to his father on his shoulder without delay. Another example of the same idea is Aaron's meeting Moses when the latter returned from Midian to assume the leadership of the Jewish people. Aaron's joy and lack of envy of his younger brother is extolled by the Torah in Exodus 4,14. The Midrash adds that if Aaron had known that the Torah would compliment him on his deed, he would have organised a musical band to welcome Moses home to Egypt instead of merely going to meet him all by himself. The Midrash goes on with a similar comment about the way Boaz treated Ruth amongst the gleaners (Ruth 2,14). Boaz is reported there as inviting Ruth to dip her morsel in vinegar. Had he known that this gesture would have been recorded in Scripture for all to know, he would have offered her all kinds of delicacies.