Answered by Shaykh Amjad Rasheed
Is it permitted to give clothes to wash in the general laundrettes, with the clothes of non-Muslims, given the possibility that their clothing could be filthy?
Walaikum assalam wa rahmatullah,
Yes, it would be permitted, and pure clothing would not be considered to have thereby become filthy, unless we are certain that the clothing of non-Muslims or others (of those who do not avoid filth) was in fact filthy.
It is established in Sahih Bukhari and Sahih Muslim from Imran ibn Husayn (Allah be pleased with him) that the Prophet (peace and blessings be upon him) and his Companions performed ablutions (wudu) from the leather container of a polytheist woman.
However, it is best (afdal) to exercise caution and to avoid such matters. As for the actions of the Prophet (peace and blessings be upon him), they were to show permissibility.