A stairway to heaven
The "stairway to heaven" is another term for Jacob's ladder, which appears in a famous biblical story in Genesis 28:11-19.
The story of Jacob's ladder is that Jacob falls asleep on his way between Beersheba and Haran and dreams of a ladder climbing up to heaven, with angels ascending and descending along it.
The Lord then says to him, "the land on which you lie I will give to you and to your descendants; and your descendants shall be like the dust of the earth, and you shall spread abroad to the west and to the east and to the north and to the south; and by you and your descendants shall all the families of the earth bless themselves. Behold, I am with you and will keep you wherever you go, and will bring you back to this land; for I will not leave you until I have done that of which I have spoken to you."
Then Jacob wakes up from his sleep and says, "Surely the Lord is in this place; and I did not know it… This is none other than the house of God, and this is the gate of heaven."
And she's buying a stairway to heaven
What's that mean? How do you buy a stairway to heaven? A stairway to heaven is usually thought to be something attained through virtue, not bought at a hardware store.
In Christian theology the stairway to heaven (Jacob's ladder) can be thought of as one of two things: the ascension to heaven through a person's own virtuous acts, or Jesus Christ himself—as in "Jesus is the path to heaven."
Either way, you can't exactly buy a stairway to heaven.
Rings of smoke through the trees
And the voices of those who stand looking
Robert Plant's lyrics echo themes that the Romantic poets explored back in the day. "Rings of smoke through the trees" is notably similar to the line "wreaths of smoke...from among the trees" in Wordsworth's "Tintern Abbey."
In truth, the lyrical themes and sonic disruption of heavy metal (yes, Led Zeppelin can actually be called heavy metal) have quite a few ties to Romanticism. The Romantic poets—think Coleridge, Keats, and Wordsworth—wrote about nature and beauty with particularly mystical, folksy, and mythological images and themes in mind.
Perhaps more importantly, like the Romantics, Led Zeppelin songwriter Robert Plant sets his folkloric images against his apprehensions about what you might call the contemporary, consumerist, or urban—namely "a lady we all know" who's "buying a stairway to heaven."
And furthermore, both the Romantics and these early heavy metal rockers popularized and pioneered new forms to get their message out. With the Romantics it was the lyric; with Led Zeppelin, it was the metal.
Then the piper will lead us to reason
Pipers have a rich history in literature. One story you've probably heard of is that of "The Pied-Piper of Hamelin."
The story of the Pied-Piper is that once upon a time a piper came to the town of Hamelin promising to clear away all the rats in the infested city. The piper uses his musical instrument to lure all the rats away from the city and into a river where they drown. When the villagers back out of their promise to pay him for his services he takes revenge by luring their children away using the same pipe.
He leads the kids into a cave and they are never seen again. (Whoa, that fairy tale is quite dark.)
It's doubtful that Robert Plant is referring here to the dangers of kids following mysterious tunes, though. The piper in this lyric seems to be another kind of rustic sign in the distance, along with "a sign on the wall," "rings of smoke through the trees," and "a bustle in your hedgerow."
Note also that the song itself begins with notes played on a recorder, which sounds a lot like an old-fashioned medieval-sounding pipe.
If there's a bustle in your hedgerow
Don't be alarmed now
It's just a spring clean for the May Queen
Chuck Eddy, who wrote Stairway to Hell: The 500 Best Heavy Metal Albums in the Universe, references this phrase as evidence of what he calls the song's "corny medievalism."
Eddy's "corny medievalism" charge probably wasn't far off the mark. The leading of the May Day parade by the May Queen was a huge tradition in Elizabethan England. But what is a May Queen—and what is May Day?
May Day is a pagan (though now Christianized) holiday in which farmers celebrate the first planting of spring. It takes place on May 1st. The May Queen (originally Diana, Goddess of the Hunt) leads the revelers through May Day eve and the morning parade in celebration. The "bustle in your hedgerow"—to which Eddy remarks, "if I found anything bustling in my hedgerow, I'd get out my shotgun"—is most likely the bustle of nymphs preparing for the festivities.
References to Greek and Roman paganism abound in medieval and Elizabethan English literature. Shakespeare's works, for example, often include nymphs and angelic, mythic beings (see A Midsummer Night’s Dream and The Tempest, for example).
When all are one and one is all
To be a rock and not to roll
This could be dismissed as meaningless wordplay, but the lyric has a lot to do with the ideas behind the song.
The Buddhist qualities of the lines here give the final verse's fervor a spiritual energy. It is in this heavy, emotional screech of rock and roll that truth can be found, it seems.
Where Plant earlier sang of double meanings and the faint voice on the "whispering wind," the "tune has come at last" with these lines, which are totally firm. Firmness is what Plant has been singing about this entire time too—the song has been "rolling" through various styles until this point, where the fever-pitch pace has finally ground the band into an idea, giving them a bedrock.