This line is from Act II, Scene 4, of King Lear in which the king pleads with Regan to allow him to live with her because her sister Goneril will only allow him a train of fifty followers. Here, however, Lear demonstrates again his flaw of judging his daughters' love mathematically. Regan informs her father that she is unprepared to take him in and he must return to Goneril. In "high rage," especially because Regan violates the order of things by telling her father to apologize to Goneril, Lear departs into a storm. Regan coldly bids Gloucester to shut the door, saying,
O, sir, to wilful men,
The injuries that they themselves procure
Must be their schoolmasters. Shut up your doors:
He is attended with a desperate train;
And what they may incense him to, being apt
To have his ear abused, wisdom bids fear. (2.4.327-332)
She accuses her father of allowing his mind to be deceived by what he thinks he hears, he is ruled by fear. Thus, in this last line there are two literary techniques at work: synecdoche and personification.
Synecdoche - the use of part of something for the whole, the "ear" represents King Lear's mind and his entire person.
Personification - the attributing of human qualities to things or ideas. Here, wisdom is personfied as it "bids," meaning it is able to command, or invite, the emotion of fear.