Sefer Ha’mitzvos Ha’Katzar (the concise book of mitzvos)
By the Chofetz Chaim
This book lists the Torah mitzvos that can be observed today
First Section – the Positive Commandments
12. It is a positive commandment to hang a mezuzah at the entrance to the house
As it says in Devarim (Deuteronomy) 6:9, “And you shall write them on the mezuzos of your house and your gates.” In the mezuzah two sections are written: Shema and Vehaya Im Shamo’a. A person is obligated to be careful with a mezuzah, and all times that a person enters or exits his house, the Unity of His blessed name will encounter him and he will remember his love for Him. He will awaken from his slumber and from his errors of wasting time. Also, he will know that nothing exists forever except the knowledge of the Rock of the world. And immediately he will return to know Him and follow His straight path.
This is obligated in all places and at all times, for men and for women.