בֶּן הֵא הֵא אוֹמֵר, לְפוּם צַעֲרָא אַגְרָא:
Бен Ха Ха говорит: По страданиям это награда. [Чем больше «страданий» вы вкладываете в труд по изучению Торы и выполнение мицвот, тем больше будет ваша награда.]
Kli Yakar
And all the other things listed in the Talmud and Midrashim have no support from this Torah passage, therefore I have seen fit to establish all the particular actions done to the metzora [person afflicted with tzara’at] on the foundation of these three things: evil speech [lashon hara], arrogance, and desire for wealth. The verse encompasses them by saying, Whoever slanders his neighbor in secret, him I will cut off; he who has haughty eyes and a proud heart, him I will not endure (Psalms 101:5). A proud heart refers to one who covets wealth, as they said (Avot 5:23) about Balaam that he had “a wide soul” [meaning he was greedy]. And him I will cut off the Sages interpreted (Arachin 15b) as referring to a confirmed metzora. The verse makes two divisions, joining haughty eyes with proud heart because both come from the same source, for the root of the eye depends on the understanding of the heart (Avodah Zarah 28b). Every haughty person has a proud heart, for every arrogant person desires great wealth through which he can display the glory of his greatness. Conversely, all wealth causes a lifting of the heart, as it is written And your silver and gold increase… and your heart becomes proud (Deuteronomy 8:13-14). Evidence of this is from what Elisha said to Gehazi, May the leprosy of Naaman cling to you (2 Kings 5:27). Why did he need to mention Naaman’s leprosy? Because Gehazi was coveting wealth (see 2 Kings 5:20-24), and Naaman was haughty. The commentators learned this from what is written Naaman, commander of the army of the king of Aram, was a great man in the sight of his master (2 Kings 5:1). This means that even in the presence of his master, he conducted himself with greatness and pride. We have already said that arrogance and greed come from the same source, therefore he said, May Naaman’s leprosy cling to you. Similarly, David joined them together saying, he who has haughty eyes and a proud heart, etc.
Or HaChaim
If you were to ask why G'd would have created a tree that was poisonous at all, the answer is -as in many such instances- that the greater the physical and spiritual effort to overcome such potential impediments to our faith, the greater the reward which is stored up in heaven for such acts of faith, a reward to be consumed by us in the Hereafter. This concept is phrased in Avot 5,26: לפום צערא אגרא, as "the reward is commensurate with the effort expended." Had G'd imposed strict limits on the power of the seducer to entice us, overcoming him would not have amounted to much. The Zohar illustrates this principle by the example of a father who wanted to test his son's moral fibre and who instructed a beautiful harlot to use all her wiles to seduce him. At the same time he had instructed the son to keep his distance from the harlot in question.
Rashi
They were lighter then eagles. To do the will of their Creator.20Rashi is paraphrasing Pirkei Avos 5,23.