Stanza I Summary

Get out the microscope, because we’re going through this poem line-by-line.

Little lamb, who made thee?

The speaker addresses the lamb and asks, "Who made thee?"
The speaker is not someone who takes things as they are. He wants to know where they come from. He sounds genuinely curious, but he also places himself above the lamb by calling it "little."

Does thou know who made thee,

The speaker repeats his question in a slightly different way. He's all about using those old-sounding English words like "dost" and "thee."
Unlike in line 1, where the speaker seems curious, here he sounds like he knows the answer to the question – "Who made thee?" – and is quizzing the lamb. We get the sense that we're going to learn the answer before too long.

Gave thee life, and bid thee feed
By the stream and o'er the mead;

These lines extend the question of "Who?"
The speaker wants to know who gave the lamb life and that voracious appetite for greenery that leads it to travel by streams and over meadows, or "mead." Put this way, the lamb sounds kind of like a zombie. Instead of busting through windows and shouting, "Braiiins!", it runs through flowery fields and bleats, "Graaaass!"
In other words, the lamb didn't create its own desires and appetites. They come from a higher power.

Gave thee clothing of delight,
Softest clothing, woolly, bright;

The lamb has a creator who gave it "clothing of delight," which sounds like the next high-end fashion line. This clothing is advertised as "the softest" and "wooly bright."
The speaker doesn't seem to mind the redundancy of describing lamb's wool as "wooly." That's like calling someone's hair "hairy." Not too helpful.
The wool looks "bright" because it gleams in the sun.

Gave thee such a tender voice,
Making all the vales rejoice?

Line 7 is the third in this stanza to begin with the word "Gave."
This is one lucky little lamb. As if its fancy clothing weren't enough, it also has a voice so "tender" that it makes the valleys happy as its baa-ing echoes through them.
A "vale" is just a word for valley. When the lamb speaks, the valleys seem to reply with the same joyful voice.

Little lamb, who made thee?
Does thou know who made thee?

In the words of Mr. Justin Timberlake, "Bring it to the chorus!"
That's right, you might be shocked to learn, but the "Songs of Innocence" are actually structured like…songs! These lines repeat word for word the first two lines of the poem. Everybody sing along now.