Al-Zuhri (may Allah have mercy on him) said: Some people of knowledge told us that Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) used to narrate that the Messenger of Allah (peace and blessings be upon him) said: "By the One in Whose Hand is my soul, the distance from the edge of the Fire to its bottom is such that if a rock, weighing as much as seven pregnant she-camels together with their fat, their flesh and their young, fell into it from the edge of the Fire, it would keep falling for seventy years before it reached its bottom."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17496