The original ruling on things is purity
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The third question of the fatwa number ( 2217 )
Q3: When one of us moves from one apartment to another, noting that all or most apartments are furnished—meaning the flooring—is it permissible for one of us to pray on what has been spilled or scattered on them, namely intoxicants, due to our lack of knowledge about the previous residents, whether they were Muslims or not?
A3: Praise be to Allah alone, and blessings and peace be upon His Messenger, his family, and his Companions.. And after: The original ruling on things is purity, so one does not rule that a thing or a place is ritually impure except with evidence indicating that this thing is ritually impure, and that this specified impurity is present in this place. If these two conditions are not met, then the Muslim prays, and his prayer is valid.
And success is from Allah, and may Allah send prayers and blessings upon our Prophet Muhammad and his family and his Companions.
Source
www.alifta.gov.sa
The Arabic text is copied verbatim from the original source, without any edits.