When one earns a livelihood, his success is from Hashem's hashgachah, not from the rules of nature.
It states (Shemos 23:13) "Concerning all that I have said to you, you shall beware to keep..." The pasuk doesn't clarify what Hashem said to us, and which command Hashem warns us to keep. At the end of the pasuk it states "The name of avodah zarah you shall not mention; it shall not be heard through your mouth." How does the end of the pasuk connect with the beginning of the pasuk?
Orach l'Chaim (from the Rebbe of Zlotchev zy'a) answers: Hashem obligates us to make hishtadlus, so everything will appear to be happening according to nature. This is the reason it states (Devarim 14:29) "Hashem your G-d will bless you in all the work of your hand that you will do." The pasuk is telling us that Hashem will give us parnassah, but the pasuk adds "that you must do." The Sifri (Re'eh) learns from these words that we must do hishtadlus, so the world will appear to be running according to the rules of nature. Similarly, it states (Tehillim 104:23) "Man goes out to his work, to his labor until evening." A person is obligated to make an effort. There are many other pasukim like this.
Orach l'Chaim warns that a person should not think that the rules of nature have strength in and of themselves. For example, one mustn't think that "if I employ this method of hastening, I will succeed, and if I don't, I won't succeed." Instead, we must believe with emunah sheleimah that Hashem gives parnassah, and not nature.
If a person thinks that the rules of nature have some strength, it is as if he is saying that there is a power other than Hakadosh Baruch Hu, the Creator of all worlds. It is like he believes in the strength of "elohim acherim," avodah zarah, chas veshalom.
With this introduction, Orach l'Chayim explains the pasuk we began with: The pasuk is obligating us to believe that everything that occurs, it was Hashem's decree. It didn't happen due to the rules of nature.
We now go on to explain the end of the pasuk, "The name of elohim acheirim (avodah zarah) you shall not mention; it shall not be heard through your mouth." Nature, is gematriya Elokim (86). When one believes in nature, it is like he believes in elohim acherim, avodah zarah. The pasuk states, "Be cautious that you don't believe in nature, for that is like believing in elohim acherim, avodah zarah, r'l."
Reb Shlomo Zalman Auerbach zt'l explains that when a person trusts in his work as an entity on its own and thinks that he will earn his livelihood from it, that is akin to worshipping avodah zarah. What is the difference between him and an idol worshipper? Idol worshippers also believe that Hakadosh Baruch Hu created the world, but they think that the stars have the power to bring bounty, parnassah, and their other needs (as the Rambam writes). It is the same when someone trusts in his work. Essentially, he worships his work. He thinks that his salvation comes from his labor. A person should believe that his work is a channel and a means through which Hashem provides his sustenance. But he will receive everything that he needs, regardless of whether he works or not. Only he is obligated to make hishtadlus, and act according to the ways of the world.
These ideas aren't limited to mussar sefarim and similar works. We can also find these ideas in halachah. Shulchan Aruch HaRav (Hilchos ב"ס ו"קנ 'סי ומתן משא) writes, "A person must be cautious when he does business that he doesn't tell a lie, as it states (Vayikra 19:36) לכם יהיה צדק והין, that when he says הן, yes, it should be true, and when he says לאו, no, it should be true (see Bava Metzia 49a). Whoever tells a lie (דיבורו מחליף in his business), it is like he worshipped avodah zarah."
Why should telling a lie in business be like serving avodah zarah? The explanation is that his dishonesty proves that he doesn't believe that Hakadosh Baruch Hu gives parnassah. He thinks that he earns parnassah with his hishtadlus. This is the reason his lies can be compared to worshipping avodah zarah, r'l.
Panim Yafos zy'a (Mishpatim כסף אם ה"ד) writes that there are wealthy people who don't want to help the poor, claiming that poor people are lazy, and that if they were more energetic, they would be able to earn a living on their own. "So, why should I support them?" Panim Yafos explains that these wealthy people are mistaken because when it is bashert that someone should be poor, Hashem arranges for them to be lazy. It isn't as the rich people think, that they are poor because they are lazy. It is the opposite. Because it was decreed that they be poor, Hashem made them lazy and inactive in their pursuit of making a living. They aren't at fault; this was the decree that was placed on them.
On the same token, those who earn a lot of money are also due to Hashem’s decree. Part of the decree is that they should be energetic when it comes to earning money. The Panim Yafos says that this is hinted to in the pasuk (Devarim 8:18) "You must remember Hashem, your G-d, for it is He that gives you strength to make wealth." Hashem gives the wealthy strength, and zerizus, to earn money.
The Panim Yafos adds that in the order of the alef beis, the letters before the letters that spell כסף are עני (poverty), and the letters after כסף in the alef beis are עצל (laziness). Hashem decrees to give someone כסף, money, and together with this decree, Hashem gives him strength, to enable the person to earn the money. When Hashem decrees that a person shouldn't have כסף, the letters to the right and the left spell עצל עני, poverty and laziness. Hashem decrees on him laziness so that he will be poor.
5. I heard the following story from the baalei hamaaseh: The Zohar (vol.3 61a) states that Chiram, the king of Tzur, considered himself god, as he said about himself (Yechezkel 28:2) "I have sat in the seat of G-d." The Bas Ayin (Shabbos Chol HaMoed Pesach) asks how Chiram made this foolish mistake, to think that he is god? Even the greatest fool knows how helpless he is, and that if one of his inner organs close or open, he won't survive. So, how could he think he is god? The Bas Ayin answers, "He didn't think he was god, but he saw that he was very wealthy, wise, and had a lot of honor, and he thought that he earned it all with his own strength. Therefore, the pasuk considers it as though he made himself a god."
