Hadith: This is a stone that was thrown into Hellfire seventy years ago and it was falling into Hellfire until it reached its bottom

عَنْ أَبِي هُرَيْرَةَ رضي الله عنه قَالَ:
كُنَّا مَعَ رَسُولِ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ، إِذْ سَمِعَ وَجْبَةً، فَقَالَ النَّبِيُّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ: «تَدْرُونَ مَا هَذَا؟» قَالَ: قُلْنَا: اللهُ وَرَسُولُهُ أَعْلَمُ، قَالَ: «هَذَا حَجَرٌ رُمِيَ بِهِ فِي النَّارِ مُنْذُ سَبْعِينَ خَرِيفًا، فَهُوَ يَهْوِي فِي النَّارِ الْآنَ حَتَّى انْتَهَى إِلَى قَعْرِهَا».
[صحيح] - [رواه مسلم] - [صحيح مسلم: 2844]

Abu Hurayrah (may Allah be pleased with him) reported:
We were in the company of the Messenger of Allah (may Allah's peace and blessings be upon him) when he heard a bang. Thereupon, the Prophet (may Allah's peace and blessings be upon him) said: "Do you know what it is?" We said: "Allah and His Messenger know best." He said: "This is a stone that was thrown into Hellfire seventy years ago and it was falling into Hellfire until it reached its bottom."
[Authentic hadith] - [Narrated by Muslim] - [Sahih Muslim - 2844]

Explanation

The Prophet (may Allah's peace and blessings be upon him) heard a disturbing sound like that of a falling object. He asked the Companions who were with him about that sound, and they said: Allah and His Messenger know best.
He (may Allah's peace and blessings be upon him) said to them: This sound that you heard is a stone that was thrown from the edge of Hellfire seventy years ago, and it kept descending and going down into it until it reached its bottom now when you heard the sound.