Reread lines 16-18 (Act 2, scene 1), in which Macbeth tells Banquo that he and his wife couldn't entertain

the king as they would have liked. Why are these remarks ironic?

The following are the lines 16-18 (Act 2, scene 1), in which Macbeth tells Banquo that he and his wife couldn’t entertain the king as they would have liked.

Being unprepared,

Our will became the servant to defect,

Which else should free have wrought

= these lines are ironic because the wife of Baquo liked to entertain the king but she can't because she is not prepared. Her will to entertain may cause a mistake because she was not prepared what should be carefully done.