What Shakespeare did say

ACT 4, Scene 2
Scene 11. "KING JOHN'S palace, Salisbury.

Therefore, to be possess'd with double pomp,
To guard a title that was rich before,
To gild refined gold, to paint the lily,
To throw a perfume on the violet,
To smooth the ice, or add another hue
Unto the rainbow, or with taper-light
To seek the beauteous eye of heaven to garnish,
Is wasteful and ridiculous excess.....

(An example would be putting heavy makeup on a
beautiful young girl.)

As you can see Shakespeare never actually said the words "To gild the Lily", but like so many other things over many many years has been mis quoted, and so was born the phrase "To gild the lily."