Midras uncleanness () is one of the forms of ritual impurity in Judaism which can be transmitted by either an object or person. The term may be translated as pressure uncleanness.
A midras (lit. "trampled on" object) is 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. A person who becomes unclean 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;
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 mikveh bath (before sunset), and the subsequent elapse of sunset.
Objects that are not subject to becoming unclean as midras include;