And thou didst give Behemoth one of the parts which had been dried up on the third day, to live in it: Behemoth was assigned to live on land. For the parts which had been dried up on the third day, see verse 42.

Where there are a thousand mountains: This clause reflects Psa 50.10, which says “For every beast of the forest is mine, the cattle on a thousand hills.” The Hebrew word for “cattle” is behemoth. The writer of 2 Esdras misinterpreted the Hebrew of Psa 50.10.

Good News Bible provides a good model for this verse.

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on 1-2 Esdras. (UBS Helps for Translators). Miami: UBS, 2019. For this and other handbooks for translators see here.