Midras

The term midras uncleanness (Hebrew: טומאת מדרס‎) or pressure uncleanness is used for uncleanness transmitted by either an object or person in Judaism.

In terms of ritual purity in Judaism a midras (lit. "trampled on" object) is a Hebrew term used to denote an object that can be a carrier of ritual impurity. Common objects that could potentially become unclean, and become a such midras object, include a chair, sofa, mattress, and rug. Once a person becomes unclean, he or she is categorized as a "father of uncleanliness".

The general concept of a midras, an object becoming a carrier for uncleanliness, is brought in the book of Leviticus, though the following verse does not employ the Hebrew term midras;

Anyone who touches his bed must wash their clothes and bathe with water, and they will be unclean till evening.

According to Maimonides on Zavim 4:4, the midras object becomes unclean by a person who is a "father of uncleanliness" (such as a man with a seminal emission or a woman in the middle of menstruation) putting most of their body weight in one (or more) of five ways on the midras;

Once the midras becomes unclean, it transmits uncleanliness to clean persons or objects by one of seven ways;

The person or object who becomes unclean via the midras is categorized as a Rishon L'Tumah.

The purification of the midras object is accomplished by immersing the object in a bath (before sunset), and the subsequent elapse of sunset.

Objects that are not subject to becoming unclean as midras include;

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