Biblical Book of Job (Chapter 40, verse 15-24, New International Version): Look at Behemoth, which I made along with you and which feeds on grass like an ox. What strength it has in its loins, what power in the muscles of its belly! Its tail sways like a cedar; the sinews of its thighs are close-knit. Its bones are tubes of bronze, its limbs like rods of iron. It ranks first among the works of God, yet its Maker can approach it with his sword. The hills bring it their produce, and all the wild animals play nearby. Under the lotus plants it lies, hidden among the reeds in the marsh. The lotuses conceal it in their shadow; the poplars by the stream surround it. A raging river does not alarm it; it is secure, though the Jordan should surge against its mouth. Can anyone capture it by the eyes, or trap it and pierce its nose?

Book of Enoch [ca. 300-200 BCE ] (Chapter 60:7): And on that day were two monsters parted, a female monster named Leviathan, to dwell in the abysses of the ocean over the fountains of the waters. But the male is named Behemoth, who occupied with his breast a waste wilderness on the east of the garden where the elect and righteous dwell, where my grandfather was taken up, the seventh from Adam, the first man whom the Lord of Spirits created. And I besought the other angel that he should show me the might of those monsters, how they were parted on one day and cast, the one into the abysses of the sea, and the other unto the dry land of the wilderness.

Esdras [ca. 100 CE] (Book 2, 6:47-52): On the fifth day you commanded the seventh part, where the water had been gathered together, to bring forth living creatures, birds, and fishes, and so it was done. The dumb and lifeless water produced living creatures, as it was commanded, so that therefore the nations might declare your wondrous works. Then you kept in existence two living creatures that you created; the one you called Behemoth and the name of the other Leviathan. And you separated one from the other, for the seventh part where the water had been gathered together could not hold them both. And you gave Behemoth one of the parts that had been dried up on the third day, to live in it, where there are a thousand mountains, but to Leviathan you gave the seventh part, the watery part, and you have kept them to be eaten by whom you wish and when you wish.