Why is a woman not permitted to adorn herself during the waiting period (iddah)?

A woman whose husband has died is obligated to abandon adornment during her 'iddah (four months and ten days, or until she gives birth if pregnant). This includes colored clothing intended for beautification, jewelry, kohl, perfume, henna, and anything that changes the face for beautification, except what is exempted for necessity. The wisdom behind this is to show grief over the husband's departure and to magnify the marriage contract, and to prevent anything that might arouse desire or lead to proposals during the 'iddah period. As for a woman divorced revocably, she adorns herself for her husband, while scholars differed regarding the obligation for a woman divorced three times to abandon adornment. One must submit to the rulings of Allah and His Messenger (peace be upon him).