It is important to serve Hashem with temimus. Temimus means to perform Hashem's will, even when we don't understand. Temimus also means accepting how Hashem leads our lives, even when we don't understand or wish it would be different.
Noach was extremely wise. It states (6:9) חנ ךהתהל םאלקי, and the Baal HaTurim writes that the final letters spell ם"חכ, indicating Noach's wisdom. Noach would serve Hashem with temimus, as it states (6:9) איש נח תמים צדיק. Temimus goes together with wisdom. The Divrei Yisrael zt'l explains that the greatest wisdom is to serve Hashem with temimus.
The Divrei Yisrael writes that this is also alluded to in the pasuk (Mishlei 10:9) םבת הולך חבט ךיל, "He who walks with temimus walks securely." The final letters spell ם"חכ, indicating that the greatest wisdom is when one has temimus.
This is because a wise person recognizes the feebleness of his mind in comparison to Hashem's perfection. He performs Hashem's will, even when he doesn’t understand because he knows that Hashem knows what is best. Hashem knows better than him. Furthermore, he accepts his life the way Hashem leads him, even when it doesn’t make logical sense, because he knows that Hashem knows what is best for him.
The Torah (Bamidbar 7) tells us that the nesi'im donated gold and silver utensils and korbanos for the chanukas hamizbeach. Rashi explains that each of their donations had significance. One of their donations was (Bamidbar 7:19) הקדש בשקל שקל שבעים כסף אחד מזרק למנחה בשמן בלולה סלת מלאים שניהם, "one silver sprinkling basin weighing seventy shekels... filled with fine flour mixed with oil for a korban minchah." Rashi writes that the gematriya of כסף אחד מזרק is 520. This represents two things. Rashi writes, "It represents that Noach had children when he was 500 years old and that the decree of the flood began 20 years before Noach had children."
Why is it important to commemorate that the decree of the flood began 20 years before Noach had children? It is to demonstrate Noach's temimus.
The purpose of the teivah was to grant survival for mankind and animals after the flood. Noach thought he wouldn't bear children. He was already 480 when Hashem told him to build the teivah, and he didn't yet have children. So, Noach understood that he was building the teivah for others, for someone who would bear children, and not for himself, because he couldn't produce future generations. Noach built the teivah during these twenty years with temimus. He didn't ask, "Why should I build a teivah for someone else? Let this other person (whoever it is) build the teivah himself." Noach didn't ask these questions. He built the teivah with emunah and temimus, which is why these twenty years were memorialized in the nesi'im's donation.
As we wrote, temimus means to do Hashem's will, even when we don't understand the reason, and it also means to accept the life that Hashem gives us, even when we don't understand why this should be our portion. For 499 years, Noach was barren, but he didn't ask, "Why should I, the tzaddik of the generation, remain barren, while all the reshaim around me are bearing children?" He didn't ask this question because he knew that Hashem's ways are just.
Indeed, it was for his good, as Rashi (5:32) writes, "People were bearing children at the age of one hundred years. Why did Noach have to wait until he was five hundred years old? Hakadosh Baruch Hu said, 'If Noach [will bear children in his younger years, and if] his children will be resha'im, they will be destroyed in the flood, and it will be devastating for this tzaddik. And if they will be tzaddikim, I will burden him to build many teivos.' Therefore, Hashem withheld children from him until he was five hundred years old so that Yefes, his oldest son, would be younger than [one hundred], the age of punishment, when the mabul came." Noach never asked questions about Hashem's hashgachah because Noach had the most incredible wisdom – the wisdom of temimus – to know that Hashem knows what's best.
