What quotes in Shakespeare's A Midsummer Night's Dream show the theme of friendship?

The theme of friendship, particularly the theme of
betrayal within friendship, is especially expressed in Hermia and Helena's
friendship.

We repeatedly see just how close Hermia and Helena were as
children. In fact, the woods in which most of the play is set actually served as a place
where they spent a great deal of time together as children, pouring out their hearts to
each other. In contrast, now the woods is serving as the setting in which their
friendship is broken apart. We first learn that the woods is a symbol of Hermia and
Helena's childhood friendship in the opening scene when Hermia discloses her and
Lysander's plan to escape Athens, as we see in her
lines:

And in
the wood, where often you and I
Upon faint primrose-beds were wont to
lie,
Emptying our bosoms of their counsel sweet,
There my Lysander
and myself shall meet.
(I.i.219-222)

This passage
not only portrays the theme of friendship by describing how close Hermia and Helena were
as friends, it is also sets up the woods as the ironic setting of
betrayal.

It is Helena who makes the decision to betray her childhood
best friend Hermia by informing Demetrius of her and Lysander's plans to escape Athens
via the woods, as we see in Helena's line, "I will go tell him of fair Hermia's flight"
(251). Since the line portrays betrayal, it not only depicts the theme of friendship,
but it also portrays the theme of friendship betrayal.

Ironically,
even though Helena betrays Hermia, she later believes that Hermia has actually betrayed
her by joining with the men in mocking her, as we see in her
lines:

Lo, she
is one of this confederacy!
Now I perceive they have conjoin'd all
three
To fashion this false sport, in spite of me.
(III.ii.195-197)

Helena's
accusation of Hermia's betrayal in the very same woods they bonded in as children, shows
us that the woods is being used as an ironic setting to portray both friendship and the
betrayal of friendship. In this same speech we see further references to the women's
closeness as children when Helena reminds Hermia of how they used to do and share
everything together and asks Hermia if she will now break up their friendship by joining
with the men to mock Helena just for the fun of it, as we see in her lines, "And will
you rent our ancient love asunder, / To join with men in scorning your poor friend?"
(218-219).

Therefore, these references not only portray friendship as
a theme in A Midsummer Night's Dream, they further serve to portray
the betrayal of friendship as a theme.