1)
What are Sanach and Mei Megido?
1.
Rashi, from Targum Yonasan: They are places. Sisera's camp stretched from one to the other. Radak - they are in Menasheh, and they are far from each other!
2.
Malbim: In the days of Yehoshua, Yavin gathered kings and fought Yisrael in Mei Merom (Yehoshua 11:1,5). Now he gathered kings again and camped at Mei Megido.
2)
What is the meaning of "Betza Kesef Lo Lakachu"?
1.
Rashi (from Tosefta Sotah 3:14): [Kings of Kena'ani] came to help Sisera for free Malbim - just like before, they came to help Yavin for free].
2.
Radak: Any Yisrael who fell into their hands, they would not accept any amount of money [to spare him]; they would kill him.
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