Anas bin Malik reported,
The Messenger of Allah ﷺ used to pray Asr, and a person would set off to the Awali while the sun was still high. Zuhri said, "The Awali are two or three miles from Medina," and I believe he said, "or four."
Ahmad 12644
Sahihحدثنا عبد الرزاق أخبرنا معمر عن الزهري قال
أخبرني أنس بن مالك
أن رسول الله ﷺ كان يصلي العصر فيذهب الذاهب إلى العوالي والشمس مرتفعة قال الزهري والعوالي على ميلين من المدينة وثلاثة أحسبه قال وأربعة
Its chain of transmission is sahih. It previously appeared in 
12271. The narrator's statement "or three or four" refers to all the awali (outlying villages of Madinah). As for the buildings today, they have reached most of the awali, the farthest of which is four miles away, that is, six kilometers, though the nearest of them is no more than three kilometers away. I lived there for a time, and I used to walk to the sacred precinct in half an hour at an easy pace.