1)
What did Ravshake tell Melech Ashur?
1.
Radak (Melachim II, 18:14): Sancheriv had sent Ravshake with a small amount of soldiers; his words were not accepted. Ravshake returned to Sancheriv and said that Shevna made Shalom with him. It says about them "Lo Somrun Kesher l'Chol Asher Yomeru ha'Am ha'Zeh Kesher" (8:12. Even though Shevna and his followers are the majority, do not follow them. Resha'im are not included in the count - Sanhedrin 26a.)
2)
Where is Livnah?
1.
Radak (Melachim II, 18:17): It is in Eretz Yisrael. Melech Livnah is one of the kings that Yehoshua defeated (Yehoshua 12:15).
