Or HaChaim on Numbers 23:18/אור החיים על במדבר כ״ג:י״ח

1 קום בלק, "arise Balak, etc." Why did Bileam insist that Balak arise? According to our sages in Bamidbar Rabbah 20,20 that Balak made fun of Bileam who had become a toy in G'd's hands, Bileam wanted to annoy him. This is why he said to him: "get up and listen!" This leaves the question why Bileam added the word ושמע, "and listen" with the letter ו at the beginning? He may have wanted to tell Balak that he should begin to listen immediately, as soon as he stood up.

2Alternatively, the reason was because G'd had told Bileam to return to Balak. Bileam interpreted this to mean that Balak had to personally hear all that G'd would have Bileam say the next time. If Bileam had said to Balak simply: "get up, listen, etc," this would have sounded as if the reason Balak was to get up was to enable him to hear what Bileam would say while he was standing. It would not have implied that Balak had to listen. All he would have to do was to be standing. The formulation chosen by Bileam made certain tha Balak understood that he had been commanded to remain standing and to keep listening.

3One could also understand the exclamation "get up" as a compliment, i.e. it was an elevation for Balak to listen to what G'd had to say (through the mouth of Bileam). Bileam also wanted to make sure that Balak's ears would be properly attuned to what G'd had to say. Balak being granted the privilege of listening to the words of the living G'd, raised him above his previous status of divining the future by means of the צפור, the bird. This is why Bileam added: בנו צפור, "the bird is his son." Up to that time, Balak hade been the "son" of the bird, i.e. the bird had been the senior, Balak the junior. These roles would now be reversed with Balak becoming senior to the צפור.

4There is yet another way of explaining our verse. We had described two evils Bileam had in mind. 1) He wanted to curse the people of Israel and would have done so had G'd not placed a bar in his mouth preventing him from saying what he wanted to say. 2) Even while he pronounced blessings he endeavoured to phrase them in such a way that they were potential curses. It required the Holy Spirit to translate these "so-called blessings" into the real thing. Bileam was aware that Balak suspected him of blessing the Israelites willingly; he wanted to demonstrate to him that this was not the case. This is why he invited Balak to listen closely so that he could detect in the very blessings Bileam pronounced details which were not beneficial at all. In this manner Bileam hoped to prove to Balak that he was acting under compulsion by a higher force. The letter ו before the word ושמע invited Balak to listen carefully to the double entendre in Bileam's blessings. He added the word האזינה in order for Balak to become aware every time the angel twisted the bar in his mouth to prevent him from cursing Israel outright.