The purpose of washing ritually impure clothes is to remove the impurity, and this can be done by any method and with any intention. This is because removing impurity is not a devotional act that requires a specific method or the intention of seeking closeness to Allah; rather, it is an act in which such an intention is not a condition, and it is fulfilled simply by removing the impurity itself and its traces. Therefore, if washing with a washing machine removes the impurity itself and water passes over the ritually impure clothes once, purification is achieved. However, in the case of urine, it is recommended that water pass over the clothes twice, based on narrations from the Ahl al-Bayt—such as the narration of Muhammad ibn Muslim, in which it has been stated: «سَأَلْتُ أَبا عَبْدِ اللّهِ عَلَيْهِ السَّلامُ عَنِ الثَّوْبِ يُصِيبُهُ الْبَوْلُ قالَ: اغْسِلْهُ فِي الْمَرْكَنِ مَرَّتَيْنِ، فَإِنْ غَسَلْتَهُ فِي ماءٍ جارٍ فَمَرَّةً واحِدَةً»[1]; “I asked Imam al-Sadiq about a garment that has come into contact with urine. He said: ‘Wash it twice in a basin, and once if you wash it in running water,’” and also the narration of ibn Abi Ya‘fur, in which it has been stated: «سَأَلْتُ أَبا عَبْدِ اللّهِ عَلَيْهِ السَّلامُ عَنِ الْبَوْلِ يُصِيبُ الثَّوْبَ، فَقالَ: اغْسِلْهُ مَرَّتَيْنِ»[2]; “I asked Imam al-Sadiq about urine that comes into contact with a garment. So he said: ‘Wash it twice.’”

However, does washing ritually impure clothes with something other than water—such as steam or chemical liquids—purify them? If it performs the same function as water, then yes; because in the removal of impurity, water is not inherently required, but serves merely as a means to achieve the outcome. This is the view of Abu Hanifah and Dawud al-Zahiri, one of the two transmitted reports from Ahmad, the view of some of the Ahl al-Hadith, and the view of Shaikh al-Mufid and Sayyid al-Murtada from among the Shias. However, washing ritually impure clothes with water is certainly better, considering that Allah has said: ﴿وَأَنْزَلْنَا مِنَ السَّمَاءِ مَاءً طَهُورًا﴾[3]; “And We sent down from the sky purifying water,” and: ﴿وَيُنَزِّلُ عَلَيْكُمْ مِنَ السَّمَاءِ مَاءً لِيُطَهِّرَكُمْ بِهِ وَيُذْهِبَ عَنْكُمْ رِجْزَ الشَّيْطَانِ﴾[4]; “And He sends down upon you water from the sky to purify you with it and to remove from you the defilement of Satan.”

Yes, if the operating method of certain types of washing machines—or machines that wash clothes with something other than water—is unknown, one should exercise caution; because, based on the ruling of the intellect, definite impurity requires definite purification.