Rabbi Chiya says that a person that wishes to have protection wherever he goes, should avoid stepping on the water that has been poured out the front door of a house. There’s a demon that exists between the two sides of the door, facing the opening and can see everything that is done inside the house. Because of that, we shouldn’t pour water through the door. Rabbi Yitzchak says that pure waters are okay if they were poured gently, not like disposing of dirty water. If the demon by the door sees negativity, he has permission to inflict harm of the house and may curse anything he sees.
This demon controls 365 helpers, like the number of days in a year. They come out with the person as he leaves his home.
Rabbi Elazar says that the Holy One Blessed be He wanted to protect the Israelites and he established His Name in the Torah that, in its entirety, is His One Holy Name. Those who study the Torah study his name that brings them the needed protection.
“לֹא תְאֻנֶּה אֵלֶיךָ רָעָה וְנֶגַע לֹא יִקְרַב בְּאָהֳלֶךָ.”
“no harm will overtake you, no disaster will come near your home”
When the holy name that represents the faith is placed on the door, negativity can’t stay there to bring judgments on the person and his home.
The door to our home is the ‘opening’ to our ‘vessel’. The Mezuzah on the door is like a ‘firewall’ that ‘burns’ and push away negativity. Our daily studies form spiritual garments of protection around us.
Related study from DZ #2801
We should be careful from having any kind of dirty things or impurities by the opening of our homes. Water that washed the dirty floors inside should not be poured outside the door because it would desecrate the name of God on the Mezuzah. Impurities by the door leave it without protection and the demon is allowed to inflict harm. The opening to the house should always be clean to respect the name and have our protector present.
When the Mezuzah is properly installed on the doorpost, the evil inclination & demon are at the door praising the people saying;
“זֶה הַשַּׁעַר לַיהוָה צַדִּיקִים יָבֹאוּ בוֹ”
“This is the gate of YHVH; the righteous shall enter through it.”
If there is no Mezuzah then the demon and the evil inclination get greater strength. When a person comes to enter the door, they put their hands on his head and say, “Woe to this person that left the protection of his master”. From that point, that person is without protection and depends only to the mercy of God.