What is the Sharia's position and what is the advice for a man who abandoned his wife six years ago due to her poor character and her neglect of prayer, and now wishes to marry another woman, given that there is a child between them who is attached to him, and how would his life be with the second wife concerning justice?

What we advise this man is to counsel his wife and guide her with admonition, reminding her of Allah's right upon her regarding prayer. If she does not respond, then he must divorce her, because it is not permissible to keep a wife who abandons prayer, as stated by Sheikh al-Islam Ibn Taymiyyah. If she responds, then he must remind her of his right and teach her that her insolence towards him is a forbidden form of insubordination (nushooz). If she does not cease harming him, he is permitted to divorce her or keep her, while her right to maintenance and equal division of nights (qasm) is forfeited. However, it is not advisable to keep her as long as she insists on her insubordination, because that is a great trial for her. Thus, it is better to divorce her.