look like th'innocent flower, but be the serpent under't

To remember this quote use the following mnemonic.

Looks like an innocent flower

But bee

Don't be silly it's a serpent under it

"Look like th'innocent flower, but be the serpent under't." Act 1 scene 5 line 64. Or slightly rewritten "Look like the innocent flower, but be the serpent under it." 

Meaning

• Lady Macbeth is telling Macbeth to act kind and welcoming (like an innocent flower) but to hide his deadly intentions (like a serpent hiding beneath). She's encouraging him to deceive Duncan by pretending to be loyal while secretly plotting his murder.

Exam Advice

• The reference to the "serpent" carries religious undertones, alluding to the biblical snake (a symbol of the devil) that tempts Eve in the Garden of Eden. Like the serpent, Lady Macbeth is a woman tempted by evil who in turn tempts a man (Macbeth). In the bible this temptation leads to the fall of man; in Macbeth, it results in the downfall of both Lady Macbeth and her husband. 

• Appearance vs Reality - Macbeth must hide his true thoughts and act innocent, showing the tension between how people appear and what they are.

• Manipulation - Lady Macbeth is persuading Macbeth to commit murder, showing her influence over him and her ruthlessness.