Three Rings for the Elven-kings under the sky,
Seven for the Dwarf-lords in their halls of stone,
Nine for Mortal Men doomed to die,
One for the Dark Lord on his dark throne
In the Land of Mordor where the Shadows lie.
One Ring to rule them all. One Ring to find them,
One Ring to bring them all and in the darkness bind them
In the Land of Mordor where the Shadows lie.'
...
'Seven the Dwarf-kings possessed, but three he has recovered, and the others the dragons have consumed.'
'So it is now: the Nine he has gathered to himself; the Seven also, or else they are destroyed. The Three are hidden still. But that no longer troubles him. He only needs the One; for he made that Ring himself, it is his, and he let a great part of his own former power pass into it, so that he could rule all the others . If he recovers it, then he will command them all again, wherever they be, even the Three, and all that has been wrought with them will be laid bare, and he will be stronger than ever.
(LoTR, I-2)
The memory of words at the Council came back to me: words of Saruman, hal
f-heeded at the time. I heard them now clearly in my heart.
` "The Nine, the Seven, and the Three," he said, "had each their proper gem. Not
so the One. It was round and unadorned, as it were one of the lesser rings; but
its maker set marks upon it that the skilled, maybe, could still see and read."
(LoTR, II-2)
'Still it might be well for all,' said Gloin the Dwarf, 'if all these strengths were joined, and the powers of each were used in league. Other rings there may be, less treacherous, that might be used in our need. The Seven are lost to us if Balin has not found the ring of Thror which was the last; naught has been heard of it since Thror perished in Moria. Indeed I may now reveal that it was partly in hope to find that ring that Balin went away.'
`Balin will find no ring in Moria,' said Gandalf. `Thror gave it to Thrain his son, but not Thrain to Thorin. It was taken with torment from Thrain in the dungeons of Dol Guldur. I came too late.'
(LoTR, II-2)
But Sauron gathered into his hands all the remaining Rings of Power; and he dealt them out to the other peoples of Middle-earth, hoping thus to bring under his sway all those that desired secret power beyond the measure of their kind. Seven Rings he gave to the Dwarves; but to Men he gave nine, for Men proved in this matter as in others the readiest to his will. And all those rings that he governed he perverted, the more easily since he had a part in their making, and they were accursed, and they betrayed in the end all those that used them. The Dwarves indeed proved tough and hard to tame; they ill endure the domination of others, and the thoughts of their hearts are hard to fathom, nor can they be turned to shadows.
They used their rings only for the getting of wealth; but wrath and an over-mastering greed of gold were kindled in their hearts, of which evil enough after came to the profit of Sauron. It is said that the foundation of each of the Seven Hoards of the Dwarf-kings of old was a golden ring; but all those hoards long ago were plundered and the Dragons devoured them, and of the Seven Rings some were consumed in fire and some Sauron recovered.
(Silm, OF THE RINGS OF POWER AND THE THIRD AGE)
Celebrimbor, desperate, himself withstood Sauron on the steps of the great door of the Mírdain; but he was grappled and taken captive, and the House was ransacked. There Sauron took the Nine Rings and other lesser works of the Mírdain; but the Seven and the Three he could not find. Then Celebrimbor was put to torment, and Sauron learned from him where the Seven were bestowed. This Celebrimbor revealed, because neither the Seven nor the Nine did he value as he valued the Three; the Seven and the Nine were made with Sauron's aid, whereas the Three were made by Celebrimbor alone, with a different power and purpose. [It is not actually said here that Sauron at this time took possession of the Seven Rings, though the implication seems clear that he did so. In Appendix A (III) to The Lord of the Rings it is said that there was a belief among the Dwarves of Durin's Folk that the Ring of Durin III, King of Khazad-dûm, was given to him by the Elven-smiths themselves, and nothing is said in the present text about the way in which the Seven Rings came into possession of the Dwarves.]
(UT, THE HISTORY OF GALADRIEL AND CELEBORN and of Amroth King of Lórien)