Halakhah zu Jeschijahu 5:33

And when we delve more deeply into this matter, we find that in addition to its being a grave transgression in itself, it undermines all the [upper] worlds and darkens and lessens their light. For it is the habit of many men to redouble [violation of] this negative commandment many hundreds and thousands of times in the course of their lives. For even a small sin, when it is repeated many times, becomes like [thick] cart-ropes, as Isaiah exhorted (Isaiah 5:18): "Woe unto those who draw forth iniquity with cords of deceit and [who draw forth] sin as [thick as] cart-ropes." This is analogous to the instance of a silken strand which is redoubled hundreds of times. How much more so is this sin [of lashon hara], which is extremely grave in itself and which countless men tend to repeat many thousands of times in the course of their lives without taking it upon themselves to guard themselves against it — how much more so is the [corresponding] undermining [of the worlds] above without limit!

The Sages expanded upon this relatively simple motif. The Gemara, Shabbat 75a, declares, "Any person who is capable of calculating the equinoxes and the solstices, to plot and chart the movement of the celestial bodies comprising the zodiac but fails to engage in such calculations, of him the verse says, 'but the work of the Lord they do not regard and the work of His hands they do not see' (Isaiah 5:12)."⁸Indeed, R. Moshe of Coucy, Sefer Miẓvot Gadol, miẓvot aseh, no. 46, enumerates an obligation to engage in those calculations as one of the 613 commandments. That is also the position of Sefer Yere’im (Vilna, 5659), no. 260. That position is based upon the interpretation presented by the Gemara, Shabbat 75a, of the verse “You shall observe and fulfill, for it is your wisdom and understanding in the eyes of the nations” (Deuteronomy 4:6). “Which wisdom is it that [is regarded as such] in the eyes of the nations?” queries the Gemara. The immediate answer of the Gemara is: “That is, calculation of tekufot and mazalot.” The Gemara’s statement is formulated in support of the dictum of R. Samuel bar Naḥmani in the name of R. Yoḥanan: “Whence [is it derived] that it is incumbent upon a person to calculate tekufot and mazalot? As it is said ‘and you shall observe and perform etc.’” The talmudic interpretation establishing an obligation is based upon employment of the phrase “and you shall observe and perform” in the biblical verse, a term that connotes a binding imperative.
Rambam also considers the exhortation rooted in this verse to be a mandatory obligation but does not include it in his enumeration of the 613 commandments. In the introduction to his Sefer ha-Miẓvot, shoresh bet, Rambam formulates the principle that the number 613 includes only commandments that are explicitly formulated in the Pentateuch. Excluded from that catalogue of miẓvot, asserts Rambam, are all commandments derived on the basis of rabbinic hermeneutics for, declares Rambam, were these also to be included, “the number of miẓvot would equal many thousands.”
In his responsa collection, Pe’er ha-Dor, ed. R. Abraham Chaim Freimann (Jerusalem, 5694), no. 347, Rambam responds to a query regarding the purpose of the commandment with a citation of a dictum of R. Meir, “Ponder His works for from that you will recognize He who spoke and the universe came into being.” Rambam also cites that statement in Hilkhot Yesodei ha-Torah 2:2 and in Sefer ha-Miẓvot, miẓvot aseh, no. 3. The source of the dictum is probably Sifri, Deuteronomy 6:6. Cf., editor’s note, Pe’er ha-Dor, no. 347.
Ramban, in his glosses on Rambam’s Sefer ha-Miẓvot, shoresh alef, s.v. ve-hateshuvah ha-revi’i, understands that, for Rambam, the commandment is rabbinic in nature. That position is also espoused by R. Betzalel Ze’ev Shafran, Teshuvot Ravaz, Oraḥ Ḥayyim, no. 32, who asserts that Rambam omits this commandment from his list of the 613 miẓvot because he regarded it to be rabbinic in nature. That understanding of Rambam is contradicted by the comments of Rambam both in his Sefer ha-Miẓvot and in his Pe’er ha-Dor. See also R. Moshe Sofer, Teshuvot Ḥatam Sofer, VIII, Koveẓ Teshuvot (Jerusalem, 5742), no. 26.
Ramban himself asserts that the study of tekufot and mazalot is not mandatory even as a rabbinic command. Nevertheless, he regards such activity as a desideratum and explains that the statement of the Gemara is hortatory in nature urging those who are capable of doing so to engage in those calculations and to announce forthcoming astronomical occurrences to the nations of the world. A person who is conversant with the fundamentals of astronomy but who fails to explore the ordered nature of the universe is remiss. This verse, as interpreted by the Sages, censures him for not engaging in that enterprise. What is it that the Sages are underscoring in this dictum? What halakhic obligation has this individual failed to fulfill?

From the laws of the commandment is that which they, may their memory be blessed, said (Sanhedrin 57a) that it is forbidden from Torah writ to rob even the smallest amount. But the negative commandment of "you shall not rob" only applies to the value of a small coin (perutah), since the Torah only makes liable [here] for something that is money; and less than the value of a small coin is not called money. But nonetheless, it is forbidden from Torah writ - like half a measure, for which we do not administer lashes, but it is [still] a Torah prohibition. And Rambam, may his memory be blessed, wrote (Mishneh Torah, Robbery and Lost Property 1:2), "It is forbidden to rob or oppress even a gentile and an idolater. And if he robbed him or oppressed him, he must return [it]." And in the Gemara (Bava Kamma 119a), they, may their memory be blessed, said that it is even forbidden to destroy the money of, and to rob and steal from, people that it is permitted to destroy their persons, such as the heretics. And they said as the reason for this, lest proper seed will come from them and their money would go to them. And it is also possible to say that their, may their memory be blessed, intention in the distancing of this was so that a man not accustom his nature to this, as habituation to lowly and bad traits would be lack in the soul. And it is a strong 'rope to drag iniquity.'