This verse is part of Balaam's second oracle, or prophecy, delivered to Balak, the King of Moab, during the time of the Israelite's journey through the wilderness. Let's break it down:

"He took up his parable, and said...": This is a common introductory phrase in the Old Testament when someone is about to deliver a prophetic message. "Parable" here doesn't mean a story with a moral (as we often think of parables), but rather a formal, poetic, and weighty statement or pronouncement.
"Rise up, Balak, and hear!": Balaam is commanding Balak's attention. Balak needs to be alert and receptive to the message he is about to deliver. The command to "rise up" might also indicate respect or deference, or simply a call to stand and be ready.
"Listen to me, you son of Zippor.": This further emphasizes the command to pay attention. By specifically addressing Balak as "son of Zippor," Balaam is likely trying to get Balak's full and undivided attention, possibly reminding him of his lineage and responsibility.

In essence, this verse is a setup for Balaam's prophecy. It's designed to grab Balak's attention and prepare him for the important message that follows. This message will ultimately be a blessing upon Israel, which is against what Balak wants and has paid Balaam to do.