Final answer:
The line 'You always end with a jade's trick. I know you of old.' alludes to Beatrice's familiarity with Benedick's deceptive character and her sarcastic understanding of his behavior.
Step-by-step explanation:
The line "You always end with a jade's trick. I know you of old." comes from Shakespeare's play 'Much Ado About Nothing'. When Beatrice says this to Benedick, she accuses him of being dishonest—referring to the tricks of a jade, an old term for a worn-out horse that might deceitfully appear lively.
The phrase "I know you of old" suggests that Beatrice is familiar with Benedick's character from past experiences. Her words indicate a mix of sarcasm and a deep knowledge of Benedick's tendency towards playful deception.