What are the directives of the Messenger of Allah, peace and blessings be upon him, and the Holy Quran for a husband who is jealous of his wife's attachment to her ex-husband, and how can he overcome this feeling and be content with his current situation?

Whoever digs into his wife's past has contravened the Quran and the Sunnah, as Allah has forbidden asking about things which, if disclosed, would displease the inquirer. And it is from the excellence of a person's Islam that he leaves alone that which does not concern him, which includes guarding the tongue from idle talk. Furthermore, disclosing the secret of the marital relationship is forbidden, and among the worst people in rank on the Day of Judgment is a man who tells his wife his secrets and she tells him hers, and then he spreads her secrets. The cure for confusion and anxiety is by following the guidance of the Prophet, peace and blessings be upon him, who married more than one divorcee and widow, and the Companions did likewise, for they saw no fault in that. Had it been so, Allah would not have made it lawful.