Comentario citado sobre Jeremías 31:16

ואקברה שם AND I BURIED HER THERE and did not carry her even the short distance to Bethlehem to bring her into a city. I know that in your heart you feel some resentment against me. Know, however, that I buried her there by the command of God”. And the future proved that God had commanded him to do this in order that she might help her children when Nebuzaradan would take them into captivity. For when they were passing along that road Rachel came forth from her grave and stood by her tomb weeping and beseeching mercy for them, as it is said, (Jeremiah 31:15) “A voice is heard in Rama, [the sound of weeping … Rachel weeping for her children]”, and the Holy One, blessed be He, replied to her (v. 16) “There is a reward for thy work, says the Lord etc. (v. 17) for thy children will return to their own border”. Onkelos translated it (כברת ארץ) by כרוב ארעא which is a full measure of one day’s ploughing. I am of opinion that they had a definite measure which they called “one full furrow”; old French cordié. So we say, (Bava Metzia 107a) “He ploughs (כריב) and ploughs again”, and (Yoma 43b) “as much earth as a fox carries on its feet from a ploughed field (בי כרבא).”

בני יששכר, The members of the tribe of Issachar, etc. Inasmuch as the tribe of Issachar is distinguished by intensive Torah study, the Torah alluded to this in its very name, יש שכר, "there is a reward," i.e. this tribe more than any other qualifies for reward. Any benefit secured in this life other than reward for Torah study is not worth the name, as it is transient. Our sages in Berachot 28 tell us that one needs to recite a short prayer when leaving the house of study in which one acknowledges that whereas both the secular people and the Torah scholars invest a great deal of effort in their respective pursuits, the former waste their efforts, whereas the Torah students do not labour in vain. The reason is simple. All comforts and riches in this life are transient, do not accompany man to the hereafter. The reward called שכר which one receives in return for Torah study does endure and one can take it with him to the hereafter. By using the word שכר the Torah also indicates that everything in the world which G'd has created, He created only for the sake of Issachar, i.e. the people studying Torah. We find this thought already in Bereshit Rabbah 1, i.e. that the word בראשית ברא implies that G'd only created the universe for the sake of Torah, i.e. the people who study it. Another allusion contained in this verse is related to what we learned in Uktzin 3,12 that in the messianic future (or even later) G'd will make every righteous person inherit 310 "worlds." The author of that Mishnah bases this on the numerical value of the word יש, from the promise in Jeremiah 31,16 יש שכר לפעולתיך, "there is a reward for your accomplishments."