Mussar sobre Deuteronômio 11:21

6) This [(synagogue attendance)] leads to length of days, as we find (Berachoth 8): "When R. Yochanan was told that there were old men in Bavel, he wondered, saying: 'It is written (Devarim 11:21): "so that your days and the days of your children may be multiplied upon the land which the L-rd swore to your fathers" — but not outside of that land.' When it was told him, however, that they were morning and evening in the synagogue, he said: 'This is what stands in their favor'" (see there further.)

And, in truth, the expenditures for the Torah study of his sons are outside of the expenditures for sustenance fixed for him on Rosh Hashanah, as Chazal have said (Beitzah 16a): "All the sustenance for man is fixed for him from Rosh Hashanah until Yom Kippur, except expenditures for Shabbath, …and expenditures for his sons' Torah studies, which, if he gives less, he is given less [by Heaven], and if he gives more, he is given more." Come and see what Chazal have said (Kiddushin 30a): "If one teaches his son's son Torah, Scripture reckons it unto him as if he had received it on Mount Sinai, viz. Devarim 4:9: 'And you shall impart them [(words of Torah)] to your sons and to the sons of your sons," followed by (Ibid. 10): 'the day you stood before the L-rd your G-d in Chorev.'" Also, through this, he merits long life for him and his sons, it being written (Ibid. 11:19): "And you shall teach them to your sons," followed by (Ibid. 21): "So that your days be prolonged and the days of your sons, etc."

The Torah's greatest command is to see to it that its teachings expand to as many Jews as possible, certainly including one's own children, in order to perpetuate the chain of Torah knowledge in one's family. The latter is clearly stated in Deut. 11,19 and numerous other places. It is this the sages had in mind when they said (Rashi Genesis 6,9) that the principal descendants of the righteous are their good deeds. This means that it is the fondest hope of the righteous that they become fruitful and multiply in order that their children may perform good deeds such as the study of Torah for its own sake and all that results therefrom. Concerning such an attitude Solomon has said in Kohelet 12,11: "The words of the scholars are like goads and like well driven nails i.e. נטועים." Our sages understand the word נטועים here as referring to offspring. Just as a plant is called permanent when securely planted, so one's children assure one of a degree of permanence and continuity on earth by their very existence. Words of Torah have a similar characteristic. They are fruitful and multiply like an unending fountain whose waters never cease The important thing is that preoccupation with Torah should not become a sterile intellectual exercise but something dynamic, creative. This is the reason that the Rabbis said that when one teaches one's neighbor's child Torah it is as if one had begotten him, i.e. performed a dynamic life-giving act. The same applies in even greater degree to when one teaches Torah to one's own children. The earth was given to man on condition that he live according to these principles, and the atmosphere of the land of Israel is particularly suited to further Torah study. We find an allusion to this in the positioning of the verse (11,19) instructing us to teach our children Torah immediately before the verse: "so that you will enjoy long years on the land the Lord your G–d has sworn to your forefathers to give to them, etc." (11,21). This is why this dimension is mentioned in the above quoted prayer והערב נא which we recite every morning immediately following the benediction לעסוק בדברי תורה. Our sages have formulated this prayer/blessing to include both our own offspring, וצאצאינו, as well as that of others, i.e. וצאצאי עמך בית ישראל. Anyone failing to recite this benediction may find that his children themselves will not develop to be Torah scholars. If such failure occurs on a broad basis even the atmosphere of the land of Israel, which is so suited to the spread of Torah knowledge, will become "lost," i.e. it will no longer be a built-in assist to the spread of Torah. The land's characteristic is closely bound up with the scholars residing in it practicing the virtues associated with their Torah knowledge.