Wikipedia
A re'em, also reëm , is an animal mentioned nine times in the Hebrew Bible ( Job , Deuteronomy , Numbers and ; Psalms , and ; and Isaiah ) and variously translated as a unicorn or a wild ox. It was first identified in modern times with the aurochs by Johann Ulrich Duerst who discovered it was based on the Akkadian cognate rimu, meaning Bos primigenius, the aurochs, progenitor of cattle. This has been generally accepted, as it is today even among religious scholars. It has been translated in some Christian Bible translations as " oryx" and as " unicorn" in the King James Version, possibly referring to a one-horned rhinoceros such as Rhinoceros Unicornis. Some Christian creationists believe it to be a Triceratops, while others believe it is a rhinoceros.
The King James Version of the Book of Job followed the Septuagint and Jerome Vulgate in its translation unicorn:
Some Bible translations into English, including the American Standard Version and New American Standard Bible, interpret re'em as "wild ox". Re'em is also speculated to refer to the Arabian Oryx.
In Jewish folklore, the re'em was larger than a mountain and could dam the river Jordan with its dung. To survive during the deluge, Noah had to strap its horns to the side of the Ark so that its nostril could protrude into the Ark allowing the animal to breathe. King David, while still a shepherd, mistook its horn for a mountain and climbed it, then the re'em got up, carrying David up to the heavens. He prayed to God to save him, so a lion passed in front of the re'em. As the re'em bowed down to the king of beasts, David climbed off, but was threatened by the lion. He prayed again and an animal passed by so the lion could chase it and leave David unharmed.