What is the ruling on a husband telling his wife to marry someone else after he has divorced her, and is it permissible for a non-mahram man to choose from among married women?

The greatness of the Ansar's altruism is evident in the story of Sa'd ibn Ar-Rabi' and Abdur-Rahman ibn Awf, where Sa'd offered to share his wealth and his two wives with Abdur-Rahman. Allah Almighty praised them, saying: "and prefer [them] over themselves, even though they are in [dire] poverty." (Qur’an 59:9). This altruism was not limited to men but also included women. Divorcing a wife in this situation was not disliked due to a great need, which was sheltering the Muhajirun (emigrants). It never happened that Abdur-Rahman chose Sa'd's wife; rather, he invoked blessings upon Sa'd's family. The matter did not go beyond an offer, for what is important is the greatness of the Companions' altruism and their abandonment of avarice.