Comentario citado sobre Jeremías 49:15

Another part of that same Midrash understands the opening words of the verse as meaning that in this world the Jewish people would count according to the moon, i.e. that the moon is given to the Jewish people as a gift in order that they can count their months by means of it. The moon is considered as superior to the sun as it is visible by day and by night, suggesting that the Jewish people have an existence both in this world and in the world to come. The descendants of Esau, however, count in this world by means of the orbits of the sun which has been described in the Torah (Genesis 1,16) as “the great luminary.” In the future, however, this great luminary will be made subservient to those who will be called “small,” by G’d, (compare Jeremiah 49,15) “For I will make you smallest among nations, etc.” [The prophet addresses Edom, the spiritual descendant of Esau]. At that time the (previously) small luminary, i.e. the Jewish people, will become big, the nation whom G’d calls big as we read in Deuteronomy 4,8 “and which is a great nation such as this, etc.” The descendants of those who count according to the sun’s orbits will eventually be judged by means of the sun, i.e. they will be burned by the fiery heat of the sun as we know from Malachi 3,19.
The entire matter can be understood by means of a parable. A king got engaged to a lady and wrote her a marriage settlement in which he gave her a few relatively minor gifts. Once the marriage was consummated, he wrote her a contract bequeathing to her very large gifts. The relationship between G’d and the Jewish people is somewhat similar. In this world G’d got “engaged” to the Jewish people as we know from Hoseah 2,21: “I will espouse you forever.” At that stage of our relationship with G’d He gave us only the moon, as we read in our verse “this moon is for you.” However, in the days of the messiah there will occur the consummation of our relationship with G’d. We know this from Isaiah 54,5 “for He who is your mate is the One Who has made you. The Lord G’d of Hosts is His name.” When that time arrives G’d will hand over to Israel all that is spelled out in the second marital agreement. According to Shemot Rabbah end of chapter 15, this is the meaning of Daniel 12,3 “and the knowledgeable will be radiant like the brightness of the expanse of the sky.”
We find an interesting halachah in Tractate Sofrim 19,10 as well as in the Jerusalem Talmud (Berachot 9,2) that one does not recite the benediction over the new moon except on the night following the Sabbath when one is still in a state of “fragrance,” i.e. surrounded by the joyful aura of the Sabbath and wearing Sabbath garments. When reciting this benediction one is to stand at attention facing the moon and to jump up and down three times reciting the formula: “blessed be your Creator, blessed be the One Who sanctifies you. Just as I jump in your direction without being able to touch you (with harmful intent) so those who wish to harm me may jump without achieving their aim. May fear and trepidation overcome all those; since Your arm is mighty may they be struck dumb as stone” (Exodus 15,15).

בנו הקטן HIS YOUNGER SON — The unworthy and despicable one, as (Jeremiah 49:15) “For, behold, I make thee small (קטן) among the nations, and despised among men" (Genesis Rabbah 36:7).