Classical commentators have a fundamental disagreement over whether powers of sorcery really exist in this world, or are just a figment of the imagination. This general question has important ramifications for understanding the specific story of Bilam. While some exegetes adopt a literal reading of the verses which imply that Bilam had the potential to harm the Children of Israel through his witchcraft, others like Ibn Kaspi and Abarbanel explain that the primary concern was over the psychological impact Bilam's curse would have on either the Israelites or their neighbors. Finally, a third approach argues that the very purpose of the episode was to demonstrate the powerlessness of black magic and its practitioners.
Hashem prevented Bilam from cursing the Children of Israel because his curse had the potential to cause them significant damage.
Most of these commentators suggest that some humans have the ability to manipulate or access impure powers so as to bring harm to others. They suggest two variations in understanding Bilam's specific capabilities:
Magic – Iggeret HaKodesh, Ramban, and Ralbag assert that through Bilam's knowledge of magic, he was able to manipulate the celestial spheres and negatively affect individuals or nations.
Evil eye – Tanchuma and Netziv suggest that Bilam made use of the "evil eye" to bring harm on the nation.3
According to Bavli Berakhot and Seforno, Bilam did not make use of black magic but was rather privy to the one daily instant of God's anger and was able to take advantage of it.
Are magical acts independent of Hashem?
Ralbag asserts that though one can learn the art of manipulating the stars, one cannot use this knowledge to harm someone who is under Hashem's providence.4
According to Netziv, the powers of the evil eye are built into nature, and as long as Bilam was in sight of the nation,5 he could have brought them harm. Hashem, though, has power over nature, and can intervene to remove the evil eye.6
Parallel cases – There are many stories in Tanakh which suggest that there is real power in blessings/ curses or other magical practices. For instance, the actions of Rivka and Yaakov to receive Yitzchak's blessing make sense only if one assumes that there was what to be obtained by the blessing. The simple understanding of the story of Eshet Baalat HaOv also assumes special human powers, and that the lady really had the ability to bring Shemuel back to life.7
Bilam's reputation – "אֲשֶׁר תָּאֹר יוּאָר" – According to this approach, Bilam's reputation was well earned since his curses were effective.8
For Bilam – According to Seforno, the officers brought Bilam charms ("קְסָמִים"), the tools of his trade, so he could utilize them when cursing the nation.9
For the Midianites – Netziv, in contrast, suggest that the Midianites used these for themselves to foretell whether Bilam would be successful. Seeing that he was to fail, they decided to leave, and are thus not heard of in the continuation of the story.
"וָאַצִּל אֶתְכֶם מִיָּדוֹ" – This verse is understood literally to mean that Hashem saved the nation from the potential harmful effects of Bilam's words.
Did Bilam have free will? Tanchuma suggests that Hashem removed Bilam's control over what came from his mouth.
Message of the donkey episode
Humbling experience – Y. Kaufmann10 suggests that one of the problems with the art of magic is that the successful practitioner begins to think of himself as on par with God. Thus, Hashem sent the angel and donkey to dispel such thoughts from Bilam by teaching him that his powers of "sight" were not as good as he thought.
Loss of free will – According to Tanchuma, the incident was supposed to warn Bilam that just as the donkey's mouth was under the control of God, so too Bilam would only be able to say what Hashem desired.
Hashem controls all – One might alternatively suggest that the point was to teach Bilam that everything is really in the control of God, even witchcraft.
Understanding the plague at Baal Peor
Ralbag asserts that the nation's status as idolaters (as evidenced by their sin at Baal Peor) was the very reason that God's providence alone was not enough to protect them from Bilam's curse. If, though, the nation deserved punishment and Hashem was about to bring upon them a plague regardless, why did Hashem not just let the punishment come via Bilam? See below, that Ralbag suggests that Hashem wanted to ensure that the nation recognize that the plague was a punishment for sin and not merely the result of a curse, so that they would then repent.
The others might suggest that at this point in the narrative, the nation was still innocent, and therefore undeserving of any harm that might be caused by Bilam's words.
Were the Israelites aware of Balak's plans? According to this approach, whether or not the nation was aware of Balak's plan is irrelevant, as the danger was very real and present regardless.
Although Bilam's curse had no power, since both the Children of Israel and the other nations believed in its efficacy, Bilam's words had the potential to negatively affect the Israelites.
Do forces of black magic exist? Both Ibn Kaspi and Abarbanel assert that Bilam's curse would not have been able to bring damage to the Children of Israel, but for different reasons.
Curses are nonsense – Ibn Kaspi dismisses as nonsense the notion of an effective curse, saying "אין בו ממש".11
No power against Israelite merits – Abarbanel implies that the inefficacy of the curse was related to the merits of Israel and not the emptiness of magical practices. He himself does not deny the existence of magic,12 but rather asserts that Bilam really was a magician,13 an astrologer who could read the stars.14
Astrology versus Divine providence – Abarbanel asserts that the movements of the stars regulate the events that happen on earth, but if these clash with Hashem's will, Hashem's leadership of the world holds sway, and He can change the heavenly schedule to match His desires.
Who believed in the curse?
The Children of Israel – Ibn Kaspi asserts that many amongst the nation would have been anxious about Bilam's curse, believing (erroneously) that it could harm them. Though Hashem recognized that their concern was unfounded, He, nonetheless, did not want them to be nervous or frightened and so prevented Bilam from cursing.
Other nations – According to Abarbanel, since foreign nations held Bilam's curses in high regard, they would trust in his words to attack the now cursed Israelites. To prevent such attacks, Hashem not only barred Bilam from cursing, but had him bless the nation.15
Blood on doorposts – Ibn Kaspi points to the command to spread blood on the doorposts during the Plague of Firstborns, as another case where Hashem acts to calm an erroneous belief of the masses.16
Struggle over Yaakov's blessing – To highlight the weight that ancient society attached to blessings, Ibn Kaspi points to the fight of Yaakov and Esav over their father's blessing.
Bilam's reputation – "אֲשֶׁר תָּאֹר יוּאָר" – Ibn Kaspi suggests that this was a mistaken reputation while Abarbanel claims that Bilam's knowledge of the stars gave him the the ability to foretell people's futures and thus curse those who were to have misfortune and bless those who were to have good fortune.
"וּקְסָמִים בְּיָדָם" – According to Abarbanel, Balak viewed Bilam as a magician, and thus brought him magical charms.
"וָאַצִּל אֶתְכֶם מִיָּדוֹ" – Ibn Kaspi asserts that these words of Yehoshua reflect the perspective of the nation (but not reality) who truly believed that they could have been destroyed due to Bilam's curse. According to Abarbanel the statement is true by all accounts, since aborting the curse really did protect the nation as it prevented others from gaining the confidence to fight against them.
Did Bilam have free will? Abarbanel asserts that Hashem took away Bilam's ability to say what he wanted, forcing his tongue to speak, just as he had forced the tongue of the donkey.
Message of the donkey episode – Both commentators assert that the episode taught an important message regarding the supremacy of Hashem's powers, but highlight different aspects:
Ibn Kaspi maintains that this was a prophetic dream that was meant to teach Bilam that God had the power to stop Bilam from going all together, or to allow him to go but to control what emerged from his mouth.17
According to Abarbanel, the incident relayed two related messages.
Hashem trumps astrology – Bilam, having spent most of his life as an astrologer and only recently begun to prophesy, was unclear about the relationship between Hashem's providence and the system of stars and constellations. When the two were not in sync, did Hashem or astrology win out? To teach Bilam that Hashem's will is supreme, Hashem set up an analogy of the donkey (representing the astrological system) being stopped by the angel (representing God's providence).
Removal of free will – The miraculous speech of the donkey taught Bilam that just as the donkey was forced to speak against its nature, so too Bilam would have no choice but to say what Hashem put in his mouth.
Were the Israelites aware of Balak's plans? This approach only works under the assumption that Bilam's curse would have been known to the world at large. It is not clear, though, that the Israelites would necessarily have been privy to the fact that they were cursed.
No Power to Harm
Bilam's curse had no intrinsic powers and would never have come to fruition, but Hashem thwarted it nonetheless so as to prevent a desecration of His name and to show His love for Israel.
Do forces of black magic exist? Ibn Ezra asserts that there is no truth in magical practices,18 and it is for this reason that they are prohibited.
What form of desecration?
According to Ibn Ezra, R. Bachya, and Ralbag, Hashem wanted to ensure that no one attributed the plague at Baal Peor to Bilam's curse rather than recognizing it as a punishment for sin.19
Shadal asserts that the potential problem related to the prohibition against attacking Moav. Had Bilam cursed the Israelites, people would assume that his words, and not Hashem's command, is what led them to shy away from war.
Hoil Moshe, in contrast, claims that a false prophet's utterance of a curse in the name of God upon His chosen nation, is in itself a desecration.20
Bilam's reputation – "אֲשֶׁר תָּאֹר יוּאָר" – Ibn Ezra and Ralbag assert that Bilam had astrological knowledge that enabled him to recognize when misfortune/fortune was to befall, allowing him to curse or bless those whom he knew were to receive such a fate.21
"וּקְסָמִים בְּיָדָם" – These commentators maintain that the elders brought Bilam charms to aid him, for they all perceived him as a magician with the power to curse.
"וָאַצִּל אֶתְכֶם מִיָּדוֹ" – This verse is difficult for this position since the Israelites were never in any real danger or in need of salvation. Ralbag, thus, suggests that had Bilam cursed the nation, they would never repent of their sin at Baal Peor, as they would attribute their punishment to the curse and not Hashem. This would have put them into even more danger as God tried to obliterate them.22
Message of the donkey episode
Warning – R. Bachya claims that Bilam was supposed to learn from the donkey who refused to continue on the path, that he too should not be continuing on the route he set for himself. The donkey's miraculous speech was supposed to teach him not to be haughty regarding his own cursing capabilties and to recognize that just as Hashem has the power to give the donkey speech, He can take away Bilam's speech
Mockery of magic – Nechama Leibowitz23 suggests that the whole incident was meant to mock the belief in the efficacy of magic to force the hand of Hashem. Bilam who thought he could see more than the ordinary human, and that he held the power to hurt or harm in his mouth, was taught that he could not even see what his donkey could, and that his mute animal, too, could speak, but only on Hashem's command.24
Understanding the plague at Baal Peor – According to Ibn Ezra, R. Bachya,and Ralbag, specifically because Hashem was about to harm the nation, he wanted to clarify that He was the source of the punishment and not Bilam's curse.
Were others aware of Balak's plans? This position assumes that knowledge of Bilam's curse would have spread to both the nation of Israel and others. Ralbag suggests that due to the close proximity of the Israelites to Moav and their intermingling with their wives, word would have surely reached them.