Answer: "I know, Iago, / Thy honesty and love doth mince this matter, / Making it light to Cassio"
Explanation: A little later, after Iago gives an account of the fight, Othello comments, "I know, Iago, / Thy honesty and love doth mince this matter, / Making it light to Cassio" (2.3. 246-248). He means that Iago is so loyal to his friend Cassio that he has shaded the story to make Cassio appear in a better light.