The Prophet ﷺ said, "I have been commanded to migrate to a town that will devour all other towns. People call it Yathrib, but it is Madinah. It expels its impure people just as the bellows expel the impurities of iron."
حدثنا سفيان عن يحيى عن سعيد بن يسار
عن النبي ﷺ أمرت بقرية تأكل القرى يقولون يثرب وهي المدينة تنفي الناس كما ينفي الكير خبث الحديد
Its isnad is sahih. Yahya is Ibn Saeed bin Qays Ansari Tujari Madani. This hadith is a repetition of 7231, where it appeared through the route of Malik from Yahya bin Saeed. Muslim also narrated it, 1:389, through the route of Sufyan with this same isnad.