How prodigal the soul Lends the tongue vows

The much maligned Polonius in Hamlet (Act 1, Scene 3, Line 602) speaks eloquently of how passionate advocacy is no friend of the truth.

Ay, springes to catch woodcocks! I do know,
When the blood burns, how prodigal the soul
Lends the tongue vows. These blazes, daughter,
Giving more light than heat, extinct in both
Even in their promise, as it is a-making,
You must not take for fire.