Must I continue with my husband after discovering his secret marriage of five years, with his first wife's knowledge and approval?

A husband is not obliged to inform his wife of his marriage to another woman, unless the wife stipulated this in the marriage contract. He must, however, deal justly between his wives and treat them kindly. The wife should beware lest jealousy leads to the destruction of her home, and she should be patient and treat her husband kindly, for divorce demolishes the family and deprives children of a sound upbringing. She should seek Allah's help and frequently engage in His remembrance and supplication.