How we cite our quotes: (Act.Scene.Line). Line numbers correspond to the Norton Shakespeare edition.
Quote #4
NERISSA
You need not fear, lady, the having any of
these lords. They have acquainted me with their
determinations, which is indeed to return to their
home and to trouble you with no more suit, unless
you may be won by some other sort than your
father's imposition depending on the caskets. (1.2.100-105)
The casket contest for Portia's hand in marriage is a pretty risky undertaking: if a suitor chooses the wrong casket, he can never pursue marriage (with anybody) again. Here we learn that some of the suitors would rather not play this game. They clearly desired marriage (or they wouldn't have shown up), but it isn't worth the risk. This pretty much automatically disqualifies them from being worthy of marrying Portia. It seems her father was looking for someone who'd be willing to risk everything for the girl.
Quote #5
BASSANIO
Her name is Portia, nothing undervalued
To Cato's daughter, Brutus' Portia. (1.1.172-173)
This doesn't bode well as a comparison: Brutus' Portia was indeed a noble woman, but Brutus wasn't exactly the greatest husband. In Shakespeare's play Julius Caesar, Portia dies a fairly arbitrary death, and Brutus shakes it off pretty easily. Hmm.
Quote #6
PORTIA
You must take your chance,
And either not attempt to choose at all
Or swear before you choose, if you choose wrong
Never to speak to lady afterward
In way of marriage. Therefore be advised. (2.1.40-44)
It seems rather arbitrary and harsh that the condition to try for Portia's hand is that losers can never seek marriage... ever again. Still, it holds up marriage as a really serious affair and helps separate the men from the boys in terms of who's really willing to sacrifice for the chance to marry Portia.