Answer: Tayammum (dry ablution) is merely a substitute for purification with water and is permissible only when a legitimate excuse exists. Such an excuse includes being unable to find any water at all, or possessing only a small amount that is insufficient for both one’s personal needs and ablution; in that case he saves the water for his essential needs and performs tayammum instead.
The second situation is when water is present but the person is physically unable to use it because of an illness that prevents or makes the use of water difficult; here too he resorts to tayammum. This ruling is based on the Almighty’s words:
“O you who believe, when you rise to perform the prayer, wash your faces and your hands up to the elbows, wipe over your heads and wash your feet up to the ankles; and if you are in a state of major impurity, then purify yourselves. But if you are ill or on a journey, or one of you comes from relieving himself, or you have touched women and can find no water, then perform tayammum with clean earth and wipe your faces and hands with it.” ⦗Qur’an 5:6⦘
The noble verse therefore shows that tayammum is allowed only in two cases:
- The person is ill and cannot use water.
- The person is traveling and has no water for wudu or ghusl, or has only a small quantity that is insufficient for both his needs and his purification. In either of these two cases he shifts to tayammum.
If, however, someone performs tayammum without a legitimate excuse—while water is available and he is able to use it—his tayammum is invalid and so is his prayer, for he has prayed without purification. The Prophet (peace and blessings be upon him) said: “Allah does not accept the prayer of any one of you if he passes wind until he performs ablution.” Furthermore, in the cited verse Allah, exalted is He, has made purification with water a pre-condition for prayer, in the specific manner He has described.