Musar zu Dewarim 4:9

And it [Torah] is the mainstay of the life of the soul, as we find in Sifrei, Parshath Ekev." R. Shimon says (Devarim 4:9): 'Only take heed to yourself and heed your soul exceedingly.' This may be compared to [the instance of] a king who captures a bird and hands it to his servant, saying to him: 'Take care of this bird for my son. If you lose it, do not think that you have lost a one-issar (a small-coin) bird, but that you have lost your soul.' And thus is it written (Devarim 32:47): 'For it [Torah] is not an empty thing for you [Not in vain do you toil in it; great reward inheres in it]; for it is your life.'"

I am surprised that when it comes to smallpox outbreaks, which spreads from child to child, why do people not take their children out of the city? In the future, the fathers will be responsible for the deaths of their children who are nursing, and have committed no sin, and those who are weaned and have committed no sins, and died from the sickness whose fathers did not take them away [from the city]. Every man who fears god should fear every eventuality. These things that are included in protecting the body are included in the warnings of (Devarim 4:9) 'take utmost care and watch yourselves scrupulously' and this is also the way of the world to take care of one's body since it is the container that the soul is wrapped up in so it will be a throne for the soul.

“Only observe for yourself, and guard your soul diligently, lest you forget the matters that your eyes saw” (Deuteronomy 4:9). And our Rabbis, may their memory be blessed, said (Menachot 99b) [that] anyone who forgets [even] one matter from his studies violates two negative commandments. Is it possible even if his studies were too hard for him? Hence we are taught to say, “And lest they depart from your heart” (Deuteronomy 4:9). The verse is only speaking of one who causes them to depart from his heart, by being idle from Torah study and not constantly poring over it.

We further find in Avoth (3:8): "R. Meir says: 'If one forgets a single thing from his learning, Scripture accounts it to him as if he is liable for his soul, as it is written (Devarim 4:9): "Only take heed to yourself, and heed your soul exceedingly, lest you forget, etc."

A real love for one's children must be in this path — that he thinks always to guide his children in the paths of Justice, and teach them the manner of serving God. Blessed is He, according to what is said: "The father shall make known to the children Thy truth" (Is. 38:19). And it is written: "And you shall make known (the lessons of Sinai) to your children and your children's children" (Deut. 4:9). And, as it is said concerning Abraham, "For I know him to the end that he should command his children and his household after him" (Gen. 18:19).

And I know their excuses, that the times are difficult, etc. But, in truth, if they searched their souls they would know that the yetzer is only deceiving them. For in other things, which are only of physical benefit to their son, does not each one of them assist his son with all of his strength, even more than he is able? And sometimes, he even places his life in danger because of him, doing things which are against the din, both between man and his neighbor and between man and the L-rd. And he blesses himself in his heart, saying: "All will be well with me, for I am doing charity at all times by feeding my family." But when he must support his son in Torah, to know how to serve the L-rd, bringing both his son and himself to eternal life, as we shall adduce below from the midrashim of Chazal, he says that times are hard! And this is as Scripture states (Isaiah 93:2): "And not Me did you call upon, Jacob; for you grew weary with Me, O Israel" — "with Me," specifically. As we find on this verse in the Midrash, Esther Rabbah 3: "All day he is busy working and does not become weary; he prays, and he becomes weary!" 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."

From this we can learn several things. A forgetful person should make reminders for himself. And high fences are needed in order that one should not forget the Torah. As it is written, "Only take heed to thyself, and keep thy soul diligently, lest thou forget the things which thine eyes saw" (Deut. 4:9). And he must be very careful not to forget the good qualities.

And, in truth, "And if not now" implies "every hour and every day." One must think "If not now" — that the Holy One Blessed be He determines for a man every day what he is to attain of the Torah of the L-rd and His service. As to the yetzer's enticing him that tomorrow he can make up for today, this is an error. For tomorrow is an obligation in itself, and he will not be able to make up the time that he lacks now. And only from day to evening [of the same day] do we find in Chazal: "One may borrow [of his time] in the daytime and make it up [in Torah study] at night." And this is the intent of (Devarim 4:9): "And lest they depart from your heart all the days of your life." And thus, (Koheleth 9:9): "And see life… all the days of your vanity" — that is, that not one day go lost. And thus, (Rambam, Hilchoth Talmud Torah 1:10): The verse "And lest they depart from your heart all the days of your life" implies that one may not be idle in the Torah of the L-rd for even one day — until his last day. And this is intimated in the verse (Mishlei 3:28): "Do not say to your friend: 'Go and return, and tomorrow I will give you,' if you have it with you [today]." "your friend" is the good yetzer, a man's true friend, who counsels him as to what will be good for him forever.