The third scene begins sometime around 5:00 PM. The feasting and celebration have begun. Othello, who is anxious to start his honeymoon, places Cassio in charge of keeping order and watching guard over Cyprus. He warns Cassio “not to outsport discretion” (3). In other words, he is telling Cassio to remain discreet (careful, cautious) throughout the night. He is telling Cassio to remain in control and to keep order. Even though everybody else can get wild and enjoy themselves, those in charge of order and safety must be discreet. Although Cassio agrees with and accepts Othello’s command, the words soon become ironic. In very little time, Cassio will lose all control and be the exact opposite of discreet.
Cassio has a weakness. He cannot control his liquor: he gets drunk very easily (lines 29-30). Iago learns of this weakness and convinces Cassio to have just one drink to toast the wedding of Othello and Desdemona. Cassio tries to refuse, but Iago will not accept a refusal. Cassio takes the drink, and very quickly becomes quite drunk. And, thus, he loses the ability to remain discreet.
As planned earlier, Roderigo takes this opportunity to quarrel with Cassio. This action occurs offstage while Iago is talking with Montano, but quite soon Roderigo comes running across the stage with an angry Cassio chasing him (line 130).
Montano attempts to stop the drunken Cassio, but then wild Cassio starts fighting with Montano.
Roderigo uses this moment to exit.
The noise of Cassio quarreling with Roderigo and, later, Montano, is quite loud and disturbs the private honeymoon time of Othello. Obviously not pleased at having to leave Desdemona, Othello comes with some guards to stop the fighting.