This is a quote by Tybalt in Act 1, scene 1 of “Romeo and Juliet”. In the very beginning of the play, servants of the Capulet house and those of the Montague house are arguing over which family is better. The servants of the Capulet house (Sampson and Gregory) begin a sword fight with those of the Montague house (Abram and Balthazar). Eventually, Tybalt and Benvolio become involved in this dispute. While initializing a brawl between the two families, Tybalt says this to the Montagues that are present – Abram, Balthazar, and Benvolio. Tyblat actually says this quote in response to Benvolio who is trying to put an end to the fight when he says,
“Part, fools! Put up your swords. You know not what you do… I do but keep the peace. Put up thy sword, Or manage it to part these men with me.” (A. 1, s. 1)
Tybalt’s response – the quote that you are asking about – begins the brawl that gets the families into trouble with the Prince.