What is the ruling of Islamic law regarding a husband's absence from his wife for more than forty days due to work circumstances, and what should he do if he is unable to bring her to him?

Among the rights of a wife over her husband is that he should not be absent from her for more than six months, unless with her permission. This is based on the statement of Umar ibn al-Khattab: "I do not detain anyone from the armies for longer than that." Therefore, it is not permissible for a husband to be absent from his wife for more than six months, except with her permission. As for specifying the duration as forty days, that is incorrect.