Is it permissible for a man who is content with one wife and his offspring, and who lives a stable and comfortable life, to refrain from marrying another, or is marrying another considered a necessity to preserve the Sunnah of the Messenger and protect Muslim women from spinsterhood due to the large number of women?

Allah has permitted a man to marry more than one woman if he has the financial and physical ability, and does not fear injustice between them. However, this permission is not an obligation; rather, he has the choice between doing it or leaving it, unless he knows that one wife will not suffice to keep him from the unlawful. In that case, he must marry that which will keep him chaste. Among the wisdoms behind permitting polygyny is to protect Muslim women from spinsterhood, but this does not make it obligatory.