"Don’t you leave him, Samwise Gamgee"

Gandalf the Gey

Gandalf is without question, in my not always humble opinion, one of (if not the) greatest wizard in Fantasy literature. In his Book of Unfinished Tales – more properly called the Unfinished Tales of Númenor and Middle-earth – Tolkien describes him as such:

"The Enemy of Sauron, opposing the fire that devours and wastes with the fire that kindles, and succours in wanhope and distress; but his joy, and his swift wrath, were veiled in garments grey as ash, so that only those that knew him well glimpsed the flame that was within. Merry he could be, and kindly to the young and simple, yet quick at times to sharp speech and the rebuking of folly; but he was not proud, and beloved among those who were not themselves proud. Mostly he journeyed unwearingly on foot, leaning on a staff; and so he was called among Men of the North Gandalf, 'the Elf of the Wand'. For they deemed him (though in error, as has been said) to be of Elven-kind, since he would at times works wonders among them, loving especially the beauty of fire; and yet such marvels he wrought mostly for mirth and delight, and desired not that any should hold him in awe or take his counsels out of fear."

This being the case, and as is known from the mostly accurate movies, Gandalf Greyhame is a wellspring of wise quotes and his counsel quite literally saved Middle-earth. Still, I have recently come to the conclusion that possibly the most important thing he whom the Elves call Mithrandir uttered was a line we only heard twice and secondhand: "Don’t you leave him, Samwise Gamgee."
That simple line, coupled with his love for Frodo, kept Sam with the Ringbearer through fire and fear, darkness and death, and a giant spider whom  – though a black terror to all  – he bested per the strength of overpowering friendship. A friendship and companionship that Frodo needed and would have ultimately failed without; hence, by extension, making it the quote that saved Middle-earth from a second darkness. Yet, interesting, Gandalf himself did not appear to recognize the power those words wrought upon Sam.

"Then you know about Frodo!' said Gimli. "How do things go with him?"
"I cannot say. He was saved from a great peril, but many lie before him still. He resolved to go alone to Mordor, and he set out: that is all that I can say."
"Not alone," said Legolas. "We think that Sam went with him."
"Did he!" said Gandalf, and there was a gleam in his eye and a smile on his face. "Did he indeed? It is news to me, yet it does not surprise me. Good! Very good! You lighten my heart. You must tell me more. Now sit by me and tell me the tale of your journey."

Well, perhaps in typical Gandalf manner he knew and did not know simultaneously. I certainly cannot truly fathom the mind of the White Rider. Still, I think the consequences of his saying "Don’t you leave him, Samwise Gamgee" proved true another of his sayings, this time and poetically applied directly back to himself: "Even the very wise cannot see all ends."