Is the husband sinful if his wife does not pray out of laziness, or has he fulfilled his duty by advising her, and must he continue to do so?

Prayer is a great pillar of Islam, and it is the first thing a Muslim will be held accountable for. Whoever preserves it will succeed and be saved, and whoever neglects it will fail and lose. Allah Almighty has warned those who abandon prayer or are negligent in it. He says: "There succeeded them later generations who neglected prayer and pursued desires; so they are going to meet evil." (Quran 19:59) And He says: "So woe to those who pray, [but] who are heedless of their prayer." (Quran 107:4-5)

You should continue to advise your wife and explain the seriousness of abandoning prayer with wisdom and gentleness. If the advice does not benefit and she insists on abandoning prayer, then you should separate from her, due to the impossibility of establishing a Muslim household with her, and because of her potential negative influence on the children. And it is obligatory to separate from her if it is held that one who abandons prayer out of negligence and laziness is a disbeliever.