The question what Nabonidus was doing in Tema will probably remain unsolved for ever. From the following text, we may deduce that during his life time, there were strong rumors that the king suffered from a mental illness and proposed a religious reform (preferring the Moon god Sin to all other gods). These rumors were used by the author of the to explain Nabonidus' stay abroad: being mad, he ignored the supreme god Marduk and went away.
Nabonidus' devotion to the Moon is a historical fact, proven by an inscription found in Harran (in 1956). That he blasphemed against Marduk, however, must be an exaggeration.
The translation below was made by A. Leo Oppenheim and is copied from James B. Pritchard's Ancient Near Eastern texts relating to the Old Testament, 1950 Princeton. Some minor changes have been made.
The Verse Account of Nabonidus
[i.1] [As to Nabonidus:] law and order are not promulgated by him, he made perish the common people through want, the nobles he killed in war, for the trader he blocked the road.
[i.2] For the farmer he made rare the [unintelligible], there is no [lacuna], the harvester does not sing the alalu-song any more, he does not fence in any more the arable territory. [lacuna]
[i.3] He took away their property, scattered their possessions, the [lacuna] he ruined completely, their corpses remaining on a dark place, decaying.
[i.4] Their faces became hostile, they do not parade along the wide street, you do not see happiness anymore, [lacuna] is unpleasant, they decided.
[i.5] As to Nabonidus, his protective deity became hostile to him. And he, the former favorite of the gods is now seized by misfortunes. Against the will of the gods he performed an unholy action, he thought out something worthless:
[i.6] he had made the image of a deity which nobody had ever seen in this country, he introduced it into the temple, he placed it on a pedestal; he called it by the name of Moon. It is adorned with a necklace of lapis lazuli, crowned with a tiara,
[i.7] its appearance is that of the eclipsed moon, the gesture of its hand is like that of the god Lugal-[unintelligible], its head of hair reaches to the pedestal, and in front of it are placed the Storm Dragon and the Wild Bull.
[i.8] When he worshipped it, its appearance became like that of a demon crowned with a tiara, his face turned hostile [lacuna].
[ii.1] His form not even Eamummu could have formed, not even the learned Adapa knows his name.
[ii.2] Nabonidus said: "I shall build a temple for him, I shall construct his holy seat, I shall form its first brick for him, I shall establish firmly its foundation, I shall make a replica even of the temple Ekur. I shall call its name Ehulhul for all days to come.
[ii.3] When I will have fully executed what I have planned, I shall lead him by the hand and establish him on his seat. Yet till I have achieved this, till I have obtained what is my desire, I shall omit all festivals, I shall order even the New Year's festival to cease!"
[ii.4] And he formed its first brick, did lay out the outlines, he spread out the foundation, made high its summit, by means of wall decoration made of gypsum and bitumen he made its facing brilliant, as in the temple Esagila he made a ferocious wild bull stand on guard in front of it.
[ii.5] After he had obtained what he desired, a work of utter deceit, had built this abomination, a work of unholiness - when the third year was about to begin - he entrusted the army [?] to his oldest son, his first born, the troops in the country he ordered under his command.
[ii.6] He let everything go, entrusted the kingship to him, and, himself, he started out for a long journey. The military forces of Akkad marching with him, he turned to Tema deep in the west.
[ii.7] He started out the expedition on a path leading to a distant region. When he arrived there, he killed in battle the prince of Tema, slaughtered the flocks of those who dwell in the city as well as in the countryside. And he, himself, took residence in Tema, the forces of Akkad were also stationed there.
[ii.8] He made the town beautiful, built there a palace like the palace in Babylon. He also built walls for the fortification of the town and he surrounded the town with sentinels.
[ii.9] The inhabitants became troubled. The brick form and the brick basket he imposed upon them.
[iii.1] Through the hard work they [lacuna] he killed the inhabitants, women and youngsters included. Their prosperity he brought to an end. All the barley that he found therein [lacuna]
[iii.2] His tired army [lacuna] the hazanu-official of Cyrus...
[iv] [About one third of the text is missing. In the lacuna, words like "stylus" and "the king is mad" can be discerned; the sequel suggests that a Persian official made an insulting remark on Nabonidus' incapacity to write with a stylus, that war broke out, that Nabonidus had some kind of hallucinatory vision, boasted a victory over Cyrus that he actually had not won, and was ultimately defeated. The texts continues with a comparison of the pious Cyrus and the blasphemous liar Nabonidus.]
[v.1] ... the praise of the Lord of Lords and the names of the countries which Cyrus has not conquered he wrote upon this stela,
[v.2] while Cyrus is the king of the world whose triumphs are true and whose yoke the kings of all the countries are pulling. Nabonidus has written upon his stone tablets: "I have made him bow to my feet, I personally have conquered his countries, his possessions I took to my residence."
[v.3] It was he who once stood up in the assembly to praise himself, saying: "I am wise, I know, I have seen what is hidden. Even if I do not know how to write with the stylus, yet I have seen secret things. The god Ilte'ri has made me see a vision, he has shown me everything. I am aware of a wisdom which greatly surpasses even that of the series of insights which Adapa has composed!"
[v.4] Yet he continues to mix up the rites, he confuses the hepatoscopic oracles. To the most important ritual observances, he orders an end; as to the sacred representations in Esagila - representations which Eamumma himself had fashioned - he looks at the representations and utters blasphemies.
[v.5] When he saw the usar-symbol! of Esagila, he makes an [insulting?] gesture. He assembled the priestly scholars, he expounded to them as follows: "Is not this the sign of ownership indicating for whom the temple was built? If it belongs really to Bêl, it would have been marked with the spade. Therefore the Moon himself has marked already his own temple with the usar-symbol!"
[v.6] And Zeriya, the šatammu who used to crouch as his secretary in front of him, and Rimut, the bookkeeper who used to have his court position near to him, do confirm the royal dictum, stand by his words, they even bare their heads to pronounce under oath: "Now only we understand this situation, after the king has explained about it!"
[v.7] In the month of Nisannu, the eleventh day, till the god was present on his seat [lacuna]
[vi.1] [lacuna] for the inhabitants of Babylon, Cyrus declared the state of peace. His troops he kept away from Ekur. Big cattle he slaughtered with the ax, he slaughtered many aslu-sheep, incense he put on the censer, the regular offerings for the Lord of Lords he ordered increased, he constantly prayed to the gods, prostrated on his face. To act righteously is dear to his heart.
[vi.2] To repair the city of Babylon he conceived the idea and he himself took up hoe, spade and water basket and began to complete the wall of Babylon. The original plan of Nebuchadnezzar the inhabitants executed with a willing heart. He built the fortifications on the Imgur-Enlil-wall.
[vi.3] The images of the gods of Babylon, male and female, he returned to their cellas, the gods who had abandoned their chapels he returned to their mansions. Their wrath he appeased, their mind he put at rest, those whose power was at a low he brought back to life because their food is served to them regularly.
[vi.4] Nabonidus' deeds Cyrus effaced and everything Nabonidus constructed, all the sanctuaries of his royal rule Cyrus has eradicated, the ashes of the burned buildings the wind carried away.
[vi.5] Nabonidus' picture he effaced, in all the sanctuaries the inscriptions of that name are erased. Whatever Nabonidus had created, Cyrus fed to the flames!
[vi.6] To the inhabitants of Babylon a joyful heart is now given. They are like prisoners when the prisons are opened. Liberty is restored to those who were surrounded by oppression. All rejoice to look upon him as king!