months and ten days.” (1) This too is evidence that it is obligatory. Moreover, the Messenger, peace and blessings be upon him, forbade a woman whose husband has died to wear a garment containing adornment or to apply perfume, except for a small amount of qust or azfār incense after she has purified herself from menstruation, which she may use as fumigation to remove the trace of blood. Otherwise, she may not do so, as will come, if Allah wills.
Can we also infer this from his saying, peace and blessings be upon him: “It is not lawful for a woman who believes in Allah and the Last Day to mourn for a deceased person for more than three days, except for her husband: four months and ten days”? (3) Some scholars said that it may be used as evidence, because the words “it is not lawful” mean that it is prohibited, and what is prohibited can only become permissible on account of an obligation.
Other scholars said that it does not establish obligation, because the negation of lawfulness does not indicate obligation; rather, it indicates the absence of prohibition. Thus, the validity of using this proof as evidence is disputed. The basis of the disagreement is that the negation of lawfulness in the words, “It is not lawful,” does not entail obligation. This is correct; yet those scholars argued from another angle. They said: the negation of lawfulness does not indicate obligation, but it does mean prohibition, and what is prohibited can only become permissible on account of an obligation,