What are "Chayso Ya'ar"?
Radak: They are animals in forests and mountains, which are not in man's Reshus 1 . The suffix Vov in v'Chayso is extra, like in "v'Chayso Eretz l'Minah" (Bereishis 1:24), "Bno Be'or" (Bamidbar 24:3).
Malbim: They are better than an ox, and they are found Hefker.
What are "Behemos b'Harerei Elef"?
Rashi #1: It is an ox prepared for the meal in the future. Each day it grazes on 1000 mountains 1 , and at night [the grass] sprouts again.
Rashi #2: Some say that [they are animals] on 1000 mountains, or [a mountain] 1000 Parsa'os 2 land, or there are 1000 bulls there 3 .
Rashi #3: This is like "Shegar Alafecha" (Devarim 7:13), i.e. mountains full of cattle.
Radak: [Animals on] 1000, i.e. many mountains, on which you do not go. "B'Harerei" is not Samuch; it is like b'Harerim. We find like this - "Chalonei Shekufim Atumim" (Melachim I, 6:4) is like Chalonim.
Malbim: If you will say that I want specifically Behemos (as opposed to Chayso Ya'ar), I have Behemos in Harerei Elef.
Pirkei d'R. Eliezer 11, Vayikra Rabah 22:11: They also crouch on 1000 mountains.
A Parsah is four Mil (about four kilometers).
What is noteworthy that Hashem has 1000 bulls? Shlomo offered 22,000 cattle on the day of Chinuch ha'Bayis! If each animal were the size of 1000 bulls, this would be noteworthy - but Rashi's words do not imply like this. (PF)
