Ablution is mentioned in the Quran in these verses:

[4:43] O you who believe, do not observe the Contact Prayers (Salat) while intoxicated, so that you know what you are saying. Nor after sexual orgasm without bathing, unless you are on the road, traveling; if you are ill or traveling, or you had urinary or fecal-related excretion (such as gas), or contacted the women (sexually), and you cannot find water, you shall observe Tayammum (dry ablution) by touching clean dry soil, then wiping your faces and hands therewith. God is Pardoner, Forgiver.

[5:6] O you who believe, when you observe the Contact Prayers (Salat), you shall: (1) wash your faces, (2) wash your arms to the elbows, (3) wipe your heads, and (4) wash your feet to the ankles. If you were unclean due to sexual orgasm, you shall bathe. If you are ill, or traveling, or had any digestive excretion (urinary, fecal, or gas), or had (sexual) contact with the women, and you cannot find water, you shall observe the dry ablution (Tayammum) by touching clean dry soil, then rubbing your faces and hands. God does not wish to make the religion difficult for you; He wishes to cleanse you and to perfect His blessing upon you, that you may be appreciative.

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