In Act 3 Scene 2, what are some similarities with Macbeth's speech ("Come seeling night..." 46-55) and Lady Macbeth's aside (Act 1 Sc 5)?
In each of these speeches, both Macbeth and Lady Macbeth are contemplating murder (he for Banquo and Fleance, she for Duncan).
Both are appleaing to darkness so that their deeds might not be seen. Considering both scenes and their symbolism, darkness represents evil, passionate emotions, and the supernatural. Since murder is so unnatural and evil, it can only be properly achieved in the dark.
Macbeth and Lady Macbeth also appeal to supernatural spirits (evil spirits) that reside in nature and darkness to change them and eliminate any cowardly emotions they might have. While Macbeth asks "with thy bloody and invisible hand/Cancel and tear to pieces that great bond/Which keeps me pale" (3.2.51-3), Lady Macbeth asks the spirits to "unsex me here" (1.5.41). Each is asking the supernatural beings that might be listening to rid them of the traits that would stop them from committing their crimes. In Macbeth's case he is wishing to have his conscience silenced so that he will not doubt or grieve while Lady Macbeth is literally asking to have her gender erased so that she can face the challenge of killing Duncan without the possibility of being hampered by her natural feminine instincts for kindness and gentility.