Translation:

43. O ye who believe! approach not prayers with a mind befogged until ye can understand all that ye say nor in a state of ceremonial impurity (except when travelling on the road) until after washing your whole body if ye are ill or on a journey or one of you cometh from offices of nature or ye have been in contact with women and ye find no water then take for yourselves clean sand or earth and rub therewith your faces and hands. For Allah doth blot out sins and forgive again and again.

Notes (Tafseer)

562. The reference is either to a state of intoxication or to a dazed state of mind on account of drowsiness or some other cause. Or perhaps both are implied. Before the prohibition of intoxicants altogether was promulgated, it was at least unbecoming that people should come to prayers in such a state. For prayers it is only right that we should collect our whole minds and approach Allah in a spirit of reverence.

563. The strictest cleanliness and purity of mind and body are required, especially at the time of prayer. But there are circumstances when water for ablutions is not easily obtainable, especially in the dry conditions of Arabia, and then washing with dry sand or clean earth is recommended. Four such circumstances are mentioned: the two last when washing is specially required; the two first when washing may be necessary, but it may not be easy to get water. For a man, when he is ill, cannot walk out far to get water, and a man on a journey has no full control over his supplies. In all four cases, where water cannot be got, cleaning with dry sand or dry earth is recommended. This is called Tayammum.