A Greedy nature
ויען בלעם ויאמר אל-עבדי בלק אם-יתן-לי בלק מלא ביתו כסף וזהב לא אוכל לעבר את-פי יקוק אלקי לעשות קטנה או גדולה
Bilaam answered and said to the servants of Balak: “[Even] if Balak gave me the entirety of his treasury, silver and gold, I wouldn’t be able to transgress the word of Hashem, my G-d, to do something small or large”
The Moabite King Balak had a plot to hire the sorcerer Bilaam to curse the Jews. Besides his occult abilities, Bilaam was a renowned non-Jewish prophet. He had direct communication with G-d. When Bilaam heard that Balak wanted his help, he responded in the negative. He stressed that even if Balak would give him all of the riches in the world, Bilaam admitted he couldn’t go against Hashem’s will. Rashi, quoting our Sages, tells us that this teaches us that Bilaam had a greedy nature.
We can ask a simple question on this. We are taught a somewhat similar story regarding one of our Sages. Rabbi Yossi ben Kisma was offered to move to a city devoid of Torah study. Rabbi Yossi responded that even if he was offered all the gold and silver in the world, he would only live in a city of Torah. Clearly from that story, Rabbi Yossi was exaggerating, and wouldn’t never be accused of being obsessed with money. If so, why don’t we say the same with Bilaam?
The answer is based on a story related regarding mourning. One of the Sages lost his daughter, and the Rabbis wanted to go comfort him. However, one Rabbi refused to go, for he did not approve of this mourner’s practice when comforting others. When someone would lose a loved one, this Sage would say, “Don’t be sad…nothing can be done.” This implies that if there was something that could be done to prevent their death, they would have done so. This implication is somewhat blasphemous, as it indicates the ability or desire to override Hashem’s will. As a result, the Rabbi didn’t want to comfort this Sage.
In fact, there are those who rule that it is forbidden to tell a mourner, “Nothing can be done”, due to this blasphemous implication. However, some dispute this ruling, as we see King David said similarly. When King David’s son died, he told someone, “Why should I fast? Can I bring him back?” This implied that if he could, he would. We see it must not be a blasphemous thing to say. Yet still, there are those who dispute this reading. For sure a person should do all within their power to keep someone alive, both physically and by praying and fasting. King David was saying that once his son had already died, there was no point in fasting anymore, as he did all he could.
What comes out from this is it is prohibited to say, “How can I go against Hashem?” This is blasphemous, as it implies that you want to, but can’t. Therefore, when Bilaam said that even if Balak gave him all the riches in the world, he couldn’t go against Hashem, the implications are clear. If Bilaam could go against Hashem, he would have. Why is this? It must be his intense desire for money, due to his greedy nature. However, Rabbi Yossi was different. He said that even if he was given all the money in the world, a place of Torah was more valuable to him. He was simply stressing how important Torah was to him, but in no way does that indicate a greedy nature.
 Based on Teshuvos Mayim Chaim Otzros Chaim to Numbers 22:18, by Rav Chaim Rappaport, brought by Tzitz Eliezer 21:55:3
 Numbers loc. cit.
 Ad. loc., quoting Bamidbar Rabbah 20:10, Midrash Tanchuma Balak § 6, and Tanchuma Yashan Balak § 9
 Rav Chaim Rappaport brings this question from his son-in-law
 Avos 6:9
 I would have said because it’s prohibited to judge a known wicked person favorably (Sha’arei Teshuva 3:218 and Rambam to Avos 1:6, brought by Chofetz Chaim Pesicha Aseh Be’er Mayim Chaim § 3)
 Bava Kamma 38a
 Rema in Shulchan Aruch Yoreh Deah 376:2
 Yam Shel Shlomo Bava Kamma 4:10, quoted by Taz ad. loc. § 1
 II Samuel 12:23
 Taz loc. cit.