Explain "infirm of purpose! give me the daggers the sleeping and the dead are but as pictures 'tis the eye of childhoodthis is said by lady macbeth...

In Shakespeare's Macbeth, when Lady
Macbeth tells Macbeth that he is infirm of purpose in Act 2.2, she means that he is not
solid or concrete, that he is not firm, in his determination to go through with what he
wants and needs to do.  This is an insult.  She is berating him, because he's afraid to
take the bloody daggers back to Duncan's chambers.  Of course, Macbeth was also an idiot
for bringing the murder weapons with him in the first
place.

She continues to berate Macbeth by making fun of him
in other ways for not being willing to go back to Duncan's chamber to return the
daggers.  She ridicules him by saying that a dead body is just like a picture: 
harmless, of course. 

And, she says, only a child is afraid
of a painted picture, even if it is of a devil.  That's the eye of a child and painted
devil part.

Not only does Macbeth foolishly bring the
daggers back with him to his wife, but he is afraid to take them back once she discovers
them.  And she berates and ridicules him for it.