Jami` at-Tirmidhi 2588

Abdullah bin 'Amr bin Al-'As narrated that the Messenger of Allah said:"If a pellet like this one, and he pointed to one like Al-jumjumah were to be dropped from the heavens to the earth – and it is the distance of traveling five hundred years it would reach the earth before the night-fall. But if it were dropped from the top of the chain it would travel for forty years, day and night, before it would reach its foundation or bottom.” (Hasan)