Texten tycks ange tre skäl:

1) Uppgiften utsågs enbart till Frodo

Sam och om har Sam hört att uppgiften är ensam Frodo och Frodo.

Här är flera citat bokens text:

"I think that this task is appointed for you Frodo, and that if you do not find a way, no one will."

-Elrond

"Well Frodo", said Aragorn at last. "I fear that the burden is laid upon you. You are the Bearer appointed by the Council."

-Aragorn

"...for it was appointed to me by Elrond of Imladris himself before the whole Council."

-Frodo

2) Sam visste att ringen skulle korrumpera honom och han kunde inte bära den

Av speciell anteckning tycker jag Elronds uttalande att om Frodo inte kan göra det, kan ingen. Sam blev faktiskt en ringbärare under en kort tid, men när han var i besittning av det:

He felt that he had from now on only two choices: to forbear* the Ring, though it would torment him; or to claim it, and challenge the Power that sat in its dark hold beyond the valley of shadows. Already the ring tempted him, gnawing at his will and reason. Wild fantasies arose in his mind.....in that hour of trial it was the love of his master that helped him most...he knew in the core of his heart that he was not large enough to bear such a burden.

Sam vet att han inte kan bära ringen eller förstöra den.

"Come, Mr. Frodo!" he cried. "I can't carry it for you, but I can carry you and it as well. So up you get! Come on, Mr. Frodo dear. Sam will give you a ride. Just tell him where to go, and he'll go."

3) Sam visste inte vart han skulle gå, även om han kunde bära ringen

Vidare visste Sam inte vart den skulle gå. Ja, i filmen ser det uppenbart ut, men i boken är de bara vid foten av berget när Sam börjar bära Frodo:

"Thank you, Sam", he said in a cracked whisper. "How far is there to go?" "I don't know", said Sam, "because I don't know where we're going."

* förbli: [definition: fasthållning, avstå] Observera de val som Sam ger sig inte inkluderar att förstöra ringen. Han slutsatsen är att hans enda alternativ är att behålla det, men inte använda det (som Gollum) eller utmanar Sauron.

TL; DR

För mig är den enda anledningen att Sam älskade Frodo. Han visste att ta saken medan Frodo bodde skulle vara den största tortyren för Frodo. Han inser att han inte kan göra Frodo med ringen utan att göra stor psykologisk / fysisk skada för honom. I slutändan, i stället för att bära ringen, bär han Frodo på ryggen till dörren till Mount Doom.

Lång version

Sam tar ringen när han tycker att Frodo är död

Det betyder att han inte är vettig att fullfölja uppdraget på egen hand.

När Frodo förgiftades av Shelob och Sam, trots att han hade gått bort, blev Sam överväldigad av sorg. Han kunde inte lämna "döda" Frodo men han förstod också att han var tvungen att fortsätta. Hans kamp är avbildad i Book-IV (Chapter-10) (betona min),

'What shall I do, what shall I do?' he said. 'Did I come all this way with him for nothing?' And then he remembered his own voice speaking words that at the time he did not understand himself, at the beginning of their journey: I have something to do before the end. I must see it through, sir, if you understand.

'But what can I do? Not leave Mr. Frodo dead, unburied on the top of the mountains, and go home? Or go on? Go on?' he repeated, and for a moment doubt and fear shook him. 'Go on? Is that what I've got to do? And leave him?'

'If I'm to go on,' he said, 'then I must take your sword, by your leave, Mr. Frodo, but I'll put this one to lie by you, as it lay by the old king in the barrow; and you've got your beautiful mithril coat from old Mr. Bilbo. And your star-glass, Mr. Frodo, you did lend it to me and I'll need it, for I'll be always in the dark now. It's too good for me, and the Lady gave it to you, but maybe she'd understand. Do you understand, Mr. Frodo? I've got to go on.'

'What? Me, alone, go to the Crack of Doom and all?' He quailed still, but the resolve grew. 'What? Me take the Ring from him? The Council gave it to him.'

But the answer came at once: 'And the Council gave him companions, so that the errand should not fail. And you are the last of all the Company. The errand must not fail.''Let me see now: if we're found here, or Mr. Frodo's found, and that Thing's on him, well, the Enemy will get it. And that's the end of all of us, of Lorien, and Rivendell, and the Shire and all. And there is no time to lose, or it'll be the end anyway. The war's begun, and more than likely things are all going the Enemy's way already. No chance to go back with It and get advice or permission. No, it's sit here till they come and kill me over master's body, and gets It: or take It and go.' He drew a deep breath. 'Then take It, it is!'

Så Sam tog motvilligt över denna börda. Därefter var han också tvungen att lägga på den för att fly från orkerna.

Sam är inte lätt skadad av ringens lure

He no longer had any doubt about his duty: he must rescue his master or perish in the attempt.

As Sam stood there, even though the Ring was not on him but hanging by its chain about his neck, he felt himself enlarged, as if he were robed in a huge distorted shadow of himself, a vast and ominous threat halted upon the walls of Mordor. He felt that he had from now on only two choices: to forbear the Ring, though it would torment him; or to claim it, and challenge the Power that sat in its dark hold beyond the valley of shadows. Already the Ring tempted him, gnawing at his will and reason. Wild fantasies arose in his mind; and he saw Samwise the Strong, Hero of the Age, striding with a flaming sword across the darkened land, and armies flocking to his call as he marched to the overthrow of Barad-dur. And then all the clouds rolled away, and the white sun shone, and at his command the vale of Gorgoroth became a garden of flowers and trees and brought forth fruit. He had only to put on the Ring and claim it for his own, and all this could be.

In that hour of trial it was the love of his master that helped most to hold him firm; but also deep down in him lived still unconquered his plain hobbit-sense: he knew in the core of his heart that he was not large enough to bear such a burden, even if such visions were not a mere cheat to betray him. The one small garden of a free gardener was all his need and due, not a garden swollen to a realm; his own hands to use, not the hands of others to command.

Hans hjärta är inte skadad av ringen (igen kärleken till Frodo spelar sin roll).

Sam ser att kontrollringen har över Frodo

När han äntligen räddade Frodo och gav ringen tillbaka till honom var han förvånad över att dragringen hade börjat utöva på Frodo.

'All right, Mr. Frodo,' said Sam, rather startled. 'Here it is!' Slowly he drew the Ring out and passed the chain over his head. 'But you're in the land of Mordor now, sir; and when you get out, you'll see the Fiery Mountain and all. You'll find the Ring very dangerous now, and very hard to bear. If it's too hard a job, I could share it with you, maybe?'

'No, no!' cried Frodo, snatching the Ring and chain from Sam's hands. 'No you won't, you thief!' He panted, staring at Sam with eyes wide with fear and enmity. Then suddenly, clasping the Ring in one clenched fist, he stood aghast. A mist seemed to clear from his eyes, and he passed a hand over his aching brow. The hideous vision had seemed so real to him, half bemused as he was still with wound and fear. Sam had changed before his very eyes into an orc again, leering and pawing at his treasure, a foul little creature with greedy eyes and slobbering mouth. But now the vision had passed. There was Sam kneeling before him, his face wrung with pain, as if he had been stabbed in the heart; tears welled from his eyes.

'O Sam!' cried Frodo. 'What have I said? What have I done? Forgive me! After all you have done. It is the horrible power of the Ring. I wish it had never, never, been found. But don't mind me, Sam. I must carry the burden to the end. It can't be altered. You can't come between me and this doom.'

Frodo själv förklarade för honom att det var hans öde att förstöra ringen och jag tror att Sam också såg att han inte kunde "ta" ringen utan att skada Frodo (han kände sig heller inte ledsen att göra det).

Den scen du refererade till händer i Book-Six (Chapter-3)

'I can't manage it, Sam,' he said. 'It is such a weight to carry, such a weight.'

Sam knew before he spoke, that it was vain, and that such words might do more harm than good, but in his pity he could not keep silent. 'Then let me carry it a bit for you, Master,' he said. 'You know I would, and gladly, as long as I have any strength.'

A wild light came into Frodo's eyes. 'Stand away! Don't touch me!' he cried. 'It is mine, I say. Be off!' His hand strayed to his sword-hilt. But then quickly his voice changed. 'No, no, Sam,' he said sadly. 'But you must understand. It is my burden, and no one else can bear it. It is too late now, Sam dear. You can't help me in that way again. I am almost in its power now. I could not give it up, and if you tried to take it I should go mad.'

Så här svarar Frodo själv din fråga. Han har äntligen succumbed till ringen och Sam kan inte ta den från honom med våld utan att göra Frodo allvarlig skada. Vi vet att Sam älskar Frodo för dyrt (och är också för klokt) för att försöka någonting så dumt. Således når tiden kommer, fattar han sitt beslut

'Come, Mr. Frodo!' he cried. 'I can't carry it for you, but I can carry you and it as well. So up you get! Come on, Mr. Frodo dear! Sam will give you a ride. Just tell him where to go, and he'll go.'