What is the ruling of Islamic law regarding divorcing the wife after discovering her relationship with another man via telephone, or forgiving her for the sake of the child under her care?

A woman is a dwelling for her husband, and he is a dwelling for her. The nature of a garment is to be exclusive to the one who wears it. So, whoever has a relationship with someone other than her husband is committing a clear sin. A man once came to the Messenger of Allah (peace be upon him) complaining about his wife's situation, and he told him: "Divorce her," meaning, divorce her, unless signs of remorse appear on her. If they do appear, then perhaps her remaining in the marriage bond is more appropriate.