What is "Beis ha'Rechavim"?
Rashi (from Sifri Bamidbar 78): It is the house of Yonadav ben Rechev. They descended from Yisro. Radak - they are called on the name of Rechev, for he was the greatest of the family. "Hemah ha'Kinim ha'Ba'im me'Chamas Avi Veis Rechav" (Divrei ha'Yamim I, 2:55).
Why should he speak with them?
Malbim: Amidst speaking, he will bring them to Beis ha'Yayin, and they will not realize that he intends to bring them there. Then, they would guard themselves from drinking!
Why should he bring them to Beis Hashem?
Malbim: It is to publicize the matter.
Why does it say "v'Hishkisa"? They did not drink!
Radak: He put in front of them to drink.
Malbim: Strive to get them to drink, if they will want.
