The Clod and the Pebble
"Love seeketh not itself to please,
Nor for itself hath any care,
But for another gives its ease,
And builds a heaven in hell's despair."
So sang a little Clod of Clay,
Trodden with the cattle's feet,
When a Pebble of the brook
Warbled out these metres meet:
"Love seeketh only Self to please,
To bind another to its delight,
Joys in another's loss of ease,
And builds a hell in heaven's despite."
My favorites pull rather more heavily from his Song of Experience than from his Songs of Innocence. But without both, I wouldn't get the joke of the line 'Did he who made the lamb make thee?" in The Tyger ('Little lamb, who made thee? Doest thou know who made thee?" from The Lamb)
*total gross exaggeration