Why does Le Brun refuse punch when Thisbe brings him some at the party

Sylvie orders Thisbe to bring Le Brun punch at the party. He refuses to drink any unless Thisbe has some as well. When Thisbe wonders why he does not drink he tells her that he does not drink because the cup does not come from her, it comes from her madame. He knows that madame would like him to get drunk and drink a lot of punch.