Adam Clarke on Acts 1:12

A Sabbath day's journey - See the difficulties in this verse explained in the note on Luk 24:50 (note). A Sabbath day's journey was seven furlongs and a half. Olivet was but five furlongs from Jerusalem; and Bethany was fifteen. The first region or tract of Mount Olivet, which was called Bethany, was distant from the city a Sabbath day's journey, or seven furlongs and a half; and the same distance did that tract called Bethphage extend from the city. When, therefore; our Lord came to the place where these two tracts touched each other, he there ascended, which place was distant from Jerusalem a Sabbath day's journey, as St. Luke here remarks. See the notes referred to above.