Chapter on Tayammum (Dry Ablution)
Anyone who has no water—after having looked for it and being unable to obtain it—may lawfully perform tayammum, whether traveling or resident. Likewise, whoever fears that the prayer time will expire while he is occupied in procuring water may resort to tayammum in either situation. If such a person then happens to find water within that same prayer time, he should repeat the prayer as a recommended act.

No one may perform tayammum in an urban setting merely out of fear that the funeral prayer will be missed. According to Imam Mālik, a traveler who expects to come upon water should delay tayammum until the end of the time—this is recommended—whereas one who has despaired of finding water may do tayammum at the very beginning of the time. A person whose situation falls between hope and despair may also perform tayammum. Some of Mālik’s companions have recommended tayammum for everyone at the midpoint of the time.

If a traveler who cannot locate water performs tayammum at the very start of the prayer time, his act remains valid, for he has hastened to fulfill the obligation with whatever purification was available to him.

Anyone who fears harm from using water—such as a person suffering from measles, smallpox, or multiple wounds—should perform tayammum. Similarly, if someone possesses only enough water for drinking, is thirsty, fears for his life, and has no hope of obtaining more, he is treated as one who has no water and should perform tayammum; the same ruling applies if he fears life-threatening thirst for another person.