In the pre-lslamic period of ignorance a flood of rain came and filled the valley in between the two mountains (around the Kaʿba).
جَاءَ سَيْلٌ فِي الْجَاهِلِيَّةِ فَكَسَا مَا بَيْنَ الْجَبَلَيْنِ قَالَ سُفْيَانُ وَيَقُولُ إِنَّ هَذَا لَحَدِيثٌ لَهُ شَأْنٌ