Comentario sobre Deuteronómio 28:47

מרב כל means: while you possessed all good things.

תחת אשר לא עבדת…בשמחה, "Because you did not serve…out of joy, etc." This punishment and what follows until verse 58 אם לא תשמר לעשות is for non-performance of the positive commandments of the Torah. The Torah repeats the same words in verse 58 to make certain that we appreciate which set of curses is in response to which set of sins. The reason the Torah speaks of our failure to perform the commandments out of joy is to contrast joyful מצה-performance with the absolute opposite, i.e. exile experienced amid the most depressing conditions. The Torah paints a picture of the punishment fitting the crime. The Jewish people who shook off the yoke of G'd's commandments will instead have to bear the far heavier burden of their captors' yoke around their necks.

תחת אשר לא עבדת את ה' אלוקיך בשמחה, “because you did not serve the Lord your G’d joyfully.” The Torah accuses people who do serve G’d not to have done so joyfully. A person is obligated not merely to carry out G’d’s instructions but to do so gladly, in a happy frame of mind. Joy when performing any of G’d’s commandments is considered as fulfillment of a commandment by itself, meriting additional reward. This is why one may be punished for failing to perform the commandments with a joyful heart. This is why the Torah requires that its commandments be performed with full intent and joyfully. Our sages in Midrash Ruth Rabbah 5,6 comment concerning this that if Reuven had been aware that G’d would write in the Torah concerning his attempts to save Joseph’s life from the hands of his other brothers (Genesis 37,21) that he would receive a reward not only for his deed but for the good intentions accompanying same, he would have carried Joseph on his shoulders and brought him back to his (their) father. The Torah also makes a point of underlining the joy in Aaron’s heart when he saw his brother Moses again after so many years. Had he known that his feelings would be commented upon favorably (Exodus 4,14), he would have gone out to meet his brother accompanied by an orchestra of many different musical instruments. Had Boaz known that his offering Ruth food and drink in abundance would be recorded for eternity as a good deed of his, he would have fed her the choicest parts of a fatted calf, instead of merely bread and vinegar (Ruth 2,14).