3.3 Iago: "Beware, my lord, of jealousy! / It is the green-eyed monster, which doth mock / The meat it feeds on: that cuckold lives in bliss / Who, certain of his fate, loves not his wronger"
Iago warns Othello against jealousy - he has experience with it as he is jealous of Cassio himself. Iago goes on to tell Othello that compared to the agony of jealousy, simple anger is "bliss" - he is thus tempting Othello to become angry at Desdemona rather than just jealous -