Assalaamu alaykum. What is the valley which Hell itself seeks refuge from? May Allaah reward you.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.

According to what was narrated, this is a valley known as Jubb Al-Hazan (the pit of grief). It has been reported on the authority of Abu Hurayrah that the Messenger of Allaah said, "Seek refuge with Allaah from Jubb Al-Hazan." People inquired, "O Messenger of Allaah, what is Jubb Al-Hazan?" He said, "A valley in Hell from which Hell itself seeks refuge one hundred times each day." It was said, "O Messenger of Allaah, who will enter it?" He said, "It has been prepared for reciters of the Quran who show off their deeds..." [At-Tirmithi]

At-Tirmithi declared it a ghareeb hadeeth (i.e. strange [weak] according to At-Tirmithi). The hadeeth's chain of narration includes ʻAmmaar ibn Sayf Adh-Dhabbi, whose narrations were rejected by hadeeth scholars, and this is why Al-Albaani labeled it as Dha'eef (weak).

Allaah knows best.