Why is the wife sinful if she refuses intercourse when her husband calls her to it, but the husband is not sinful if he refuses intercourse when his wife calls him to it?

What is legally required from both spouses is for each to ensure the other's chastity, and this is one of the objectives of marriage. The wife must make herself available to her husband whenever he desires, unless there is harm or she is occupied with an obligatory duty, and she sins if she does not do so.

As for the husband, it is not permissible for him to abandon the marital bed for a long time in a way that harms his wife. Scholars have differed regarding the obligation of a man to have sexual intercourse with his wife. Some said once every four days, while others said once every four months. The more correct view is that it depends on her need and his ability, as Ibn Taymiyyah said that it is obligatory for the husband to have intercourse with his wife in a reasonable manner, and this is one of her most emphasized rights.