The Messenger of Allah (sal Allahu alaihi wa sallam) said: “The lawful mourning period for a widow is four months and ten days. During this period she should not put on a colourful dress, nor use any perfume, nor bedeck herself.” [Tirmidhi]
Widows, like all other Muslims, continue to take care of their hygiene and wear clean clothes. However, during their mourning period they should not make any efforts to enhance their attractiveness by wearing colorful clothes or makeup. A widow should be extra modest in her appearance during this waiting period and even refrain from using fragrance so she is visibly in a state of mourning and her social circles do not get a chance to say a negative word about her.
To prevent her ill-repute and slander others are directed against making a secret commitment of marriage with a widow during her mourning period or deciding about the time and place of the marriage contract during the prescribed period. Proposals of remarriage should be entertained after the mourning period is over. The definition of a mourning period is also to safeguard the woman from criticism for remarrying too quickly.
The period of mourning is also to prevent confusion of paternity of children in case the widow recently conceived by her late husband and then wants to get remarried after his demise. The period of four months and ten days will allow any pregnancy to be detected since it is half the length of a normal pregnancy. In the case of a pregnant widow, the mourning period ends with her delivery of the child, whether it be more or less than four months and ten days.