We can assume that when Yaakov and Eisav were young, everyone predicted that Eisav would succeed in life and Yaakov wouldn't. Eisav had a glib tongue, and always knew how to get his way. He was a hunter, working for his parnassah. On the other hand, Yaakov Avinu was an honest person, an תם איש. Rashi writes, "A person who is not astute at deceiving is called תם." He was a אהלים יושב, which means he sat in beis medresh and learned Torah all day long. People thought that, financially, nothing would become of him.
However, Yaakov became extraordinarily wealthy and received Yitzchak's brachos for success in this world and the next world. The Or Pnei Moshe zt'l says that we learn from this that parnassah comes from Hashem's blessings, and parnassah isn’t the product of "the strength of my hand."
Rashi (27:9) writes that Rivkah had a right to take two goats from Yitzchak daily. This right was written in her kesubah. She told Yaakov to take two goats and she prepared them for Yitzchak.
Yitzchak asked Yaakov how he brought the meat so quickly. Yaakov replied (27:20) כי לפני אלקיך 'ה הקרה, "Hashem, your G-d, prepared it before me." The Zera Shimshon explains that Yaakov didn't lie, chas v'shalom, when he said Hashem prepared it for him. Yaakov didn't take anything for granted. If he had two goats, Hashem prepared them for him. The Zera Shimshon writes, "We learn from this a lesson of mussar: Every person must recognize that everything is Hashem's wonders... When he earns money, he shouldn't attribute it to his hishtadlus but to Hashem's chessed."
Hishtadlus
After World War Two, the Germans offered to give money to Jewish people, called reparations, to atone for what they did and to express their regret. There was a hot machlokes among gedolei Yisrael about whether Yidden should accept the money. Some gedolim said, "Take as much money as you can from them." Others were saying that they shouldn't think that money can atone for the atrocities they committed.
The Chazon Ish zt'l didn't give an opinion about whether people should take money, but he said, "It isn't a lack in hishtadlus if one doesn't sign up to receive the reparation money." The Tchebiner Rav zt'l said the same thing. A person is obligated to do hishtadlus, but if he wishes, he can avoid doing this particular hishtadlus.
In the same vein, if a person doesn't do hishtadlus for parnassah at the time that he designated for Torah study or tefillah, that won't be viewed as being negligent in his obligation to do hishtadlus, and he will receive the money that is due to him. The same applies to speaking during davening. If you meet someone in shul with whom you must talk about some business, and you refrain because it is in the middle of the tefillah, you won't lose money because of that. You don't have an obligation of hishtadlus at such a time.
Someone asked the Chazon Ish to describe how much hishtadlus one must do. The Chazon Ish answered that it is like knocking a nail into the wall. When the nail becomes crooked, you stop hammering on it and throw it away. The same is true with hishtadlus. When things become crooked, you know that you should stop. Crooked means dishonest business, and crooked also means when one thinks he has to work during the times he set for Torah and tefillah.
