I hate him for he is a Christian;
But more for that in low simplicity
He lends out money gratis, and brings down
The rate of usance here with us in Venice.
(I, iii)

In the first act, one aspect of Shylock's nature is clearly revealed. Here he complains that Antonio, by lending out money for free, brings down the interest rate at which he can lend money. Shylock's greed is apparent throughout the play, and statements like these help draw a caricature of what Shakspeare's audience would recognize as the stereotypical, selfish, medieval Jew.

Signior Antonio, many a time and oft
In the Rialto you have rated me
About my moneys and my usances;
Still have I borne it with a patient shrug,
For suff'rance is the badge of all our tribe;
(II, vii)

Here Shylock responds to Bassiano's request for money, pointing out that he is not deaf to all of the criticism he has endured; rather, that he turns a blind eye to it. Shylock makes a good point in this conversation with Bassiano: despite their obvious hatred for him, they come to him for help in the form of money.

'All that glisters is not gold,
Often have you heard that told;
Many a man his life hath sold
But my outside to behold:
Gilded tombs do worms infold
(II, vii)

The Price of Morocco finds this note written on a scroll when he opens the golden chest. He mistakenly equates Portia with material value, and thus the chest serves as another example of Christian values that run deeper than surface appearance. Indeed, the quote suggests that the pursuit of "gold" often leads men to their tombs.

Therefore, thou gaudy gold,
Hard food for Midas, I will none of thee;
Nor none of thee, thou pale and common drudge
'Tween man and man: but thou, thou meagre lead,
Which rather threaten'st than dost promise aught,
Thy plainness moves me more than eloquence,
And here choose I: joy be the consequence!
(III, ii)

It is Bassiano that wins Portia's hand through his demonstration of Christian value and true worth. This is the end of a long quote, in which Bassiano meditates on truth and goodness versus the superficiality of surface appeareance. Thus, gold is simply "gaudy" and plain goodness is what will bring him joy.

Commend me to your honourable wife:
Tell her the process of Antonio's end;
Say how I lov'd you; speak me fair in death;
And, when the tale is told, bid her be judge
Whether Bassanio had not once a love.
(IV, i)

One of things Shakespeare explores in Merchant is the dimension of friendship, brotherly love, and love between man and wife. Here, Antonio, believing that he is about to die, speaks to Bassiano and seems to imply that a rivalry between himself and Portia exists for loving Bassiano the most. Bassiano replies to Antonio by saying that, despite his love for Portia, he would sacrifice everything to save Antonio.

Your wife would give you little thanks for that,
If she were by to hear you make the offer.
(I, i)

Portia, in disguise as a lawyer, responds to Bassiano's remark that he would sacrifice everything to save Antonio. She rightly points out that the relationship between man and wife has value superceding brotherly love between friends.

The quality of mercy is not strain'd;
It droppeth as the gentle rain from heaven
Upon the place beneath. It is twice blest:
It blesseth him that gives and him that takes
(IV, i)

Throughout the play, Portia is in many ways Christian values personified; here, in the play's climactic scene, she sums up the major theme of Merchant of Venice, that of Christian mercy and compassion.