Amazing...

The well-known Kabbalist HaKadosh R' Shimshon of Ostropoli zt'l writes in Likutei Shoshanim, from Reb Nachman Caro, zs'l, that Gehenom (hell) has 850 rooms, gematria Tchelet תכלת. This is one of the reasons it says to wear a Tzizit with תכלת (gematria 850), for the tikun of the 850 rooms in Gehenom.

When a Tzaddik passes away from this Olam, he must pass thru all 850 rooms of Gehenom. His holiness helps the wicked to elevate. Out of the 850 rooms, the Tzaddik should not fear 580 rooms because the Mazikin and the klipot of the wicked cannot harm him. But for the remaining 270 rooms, if he goes thru them without protection, the Mazikin, the strength of the impurity, and the wicked klipot can harm him.

HaShem appointed a Malach (angel) to protect these Tzadikim. The Malach's name is Yehoshua. The malach takes wax and with it, he writes for the Tzadik אתה (you) and this protects the Tzaddik from any harm. When the Mazikin sees אתה on the Tzadik, they don't dare approach or harm him.

This is how the Tzadik goes thru the 850 rooms of Gehenom and is able to help neshamot (souls) elevate.

Rav Nachman Caro continues and says that Dovid HaMelech, zs'l, already revealed this secret but we don't understand it.

Tehillim 23;4
גַּם כִּי-אֵלֵךְ בְּגֵיא צַלְמָוֶת, לֹא-אִירָא רָע כִּי-אַתָּה עִמָּדִי;שִׁבְטְךָ וּמִשְׁעַנְתֶּךָ, הֵמָּה יְנַחֲמֻנִי
Though I walk through the valley of the shadow of death, I will fear no evil, for HaShem is with me; Thy rod and Thy staff, they comfort me.

גֵיא צַלְמָוֶת - gematria 580, the 580 rooms of Gehenom
לֹא-אִירָא רָע - gematria of רָע is 270, the 270 rooms that the Tzadik needs protection.
כִּי-אַתָּה עִמָּדִי - How does the Tzadik get protection? אַתָּה (the protection)
עִמָּדִי שִׁבְטְךָ וּמִשְׁעַנְתֶּךָ הֵמָּה - Roshei Tevot שעוה wax (the Malach writes protection with wax)
עִמָּדִי שִׁבְטְךָ וּמִשְׁעַנְתֶּךָ, הֵמָּה יְנַחֲמֻנִי - Roshe Tevot יהושע (the name of the Malach)