2 Esdras 6:47-52
(New Revised Standard Version with Apocrypha)
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; 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.
2 Baruch 29:3-4
(The Old Testament Pseudepigrapha, Vol. 1)
And it will happen that when all that which should come to pass in these parts has been accomplished, the Anointed One will begin to be revealed. And Behemoth will reveal itself from its place, and Leviathan will come from the sea, the two great monsters which I created on the fifth day of creation and which I shall have kept until that time. And they will be nourishment for all who are left.
1 Enoch 60:7
(The Old Testament Pseudepigrapha, Vol. 1)
On that day, two monsters will be parted—one monster, a female named Leviathan, in order to dwell in the abyss of the ocean over the fountains of water; 8 and (the other), a male called Behemoth, which holds his chest in an invisible desert whose name is Dundayin, east of the garden of Eden, wherein the elect and the righteous ones dwell, wherein my grandfather was taken, the seventh from Adam, the first man whom the Lord of the Spirits created.
Genesis 1:21,23 (Verse 22 0mitted. See Note Below)
(Targum Pseudo-Jonathan)
God created the great sea monsters, Leviathan and his mate, that are designated for the day of consolation, and all living creatures that creep, that the clear waters swarmed forth, according to their kinds, kinds that are clean and kinds that are not clean, and all birds that fly with wings, according to their kind, kinds that are clean and kinds that are not clean. And God saw that it was good. And there was evening and there was morning, a fifth day.
Note: In the Targum Pseudo-Jonathan, verse 22 was omitted. It remains however, in Targum Neofiti. It does not actually include the specific translation "Leviathan" so not included above.
Genesis 1:21-23
(Targum Neofiti Vol 1)
And the Lord created the two great monsters and every living creature that creeps, which the waters swarmed forth according to their species, and every bird that flies according to its species. And it was manifest before the Lord that it was beautiful and proper. And the Memra of the Lord blessed them saying: “Be strong and multiply and fill the waters in the seas, and let birds multiply upon the earth." And there was evening and there was morning: (in) the order of the work of creation, fifth day.
You will find the specific books used in this resource, hyperlinked in the titles below.
New Revised Standard Version with Apocrypha
The Old Testament Pseudepigrapha, Vol. 1
The Aramaic Bible Volume 1B - Targum Pseudo-Jonathan: Genesis
The Aramaic Bible Volume 1A - Targum Neofiti 1: Genesis
Connected study article: Gog and Magog – Ezekiel 38-39, Revelation 20 (Part 2)