Aliya Summary: This Aliya discusses the ritual impurity contracted by a man who issues a (normal) seminal discharge, the ritual impurity of a menstruating woman, and of a man who cohabits with her. All such people must immerse in a mikvah (ritual pool) in order to be purified.
Sitting on the same bed or chair as an impure woman renders you impure as well, a unique law designed to separate married people for part of a normal monthly cycle. While there might be some psychological advantages to this law (abstinence makes the heart grow fonder?), it’s also important to keep the original text in mind. Otherwise one might theorize that because we are already so connected and close these laws shouldn’t apply to us, which would be a faulty argument. It’s a law, fringe benefits aside.