Explication

Look here upon this picture and on this,

The counterfeit presentment of two brothers.

See, what a grace was seated on this brow?

Hyperion’s curls, the front of Jove himself,

An eye like Mars to threaten and command,

A station like the herald Mercury

New-lighted on a heaven-kissing hill—

A combination and a form indeed

Where every god did seem to set his seal

To give the world assurance of a man.

This was your husband. Look you now, what follows.

Here is your husband, like a mildewed ear

Blasting his wholesome brother. 
You cannot call it love, for at your age
The heyday in the blood is tame, it's humble
And waits upon the judgement; and what judgment

Would step from this to this? Sense sure you have,

Else could you not have motion. But sure that sense

Is apoplexed, for madness would not err,

Nor sense to ecstasy was ne'er so thralled,

But it reserved some quantity of choice

To serve in such a difference. What devil was ’t

That thus hath cozened you at hoodman-blind?

O shame, where is thy blush?

Rebellious hell,

If thou canst mutine in a matron’s bones,

To flaming youth let virtue be as wax

And melt in her own fire. Proclaim no shame

When the compulsive ardor gives the charge,

Since frost itself as actively doth burn,

And reason panders will.
(3.4.63-98)