A Jew was permitted to travel 2,000 cubits on the Sabbath (Exod. 16: 29 and Num. 35: 5), about 1.2 km. (¾ mile), and the Mount of Olives was within this distance from Jerusalem (Acts 1: 12).
Citation for Sabbath day's journey
Citation styles are based on the Chicago Manual of Style, 15th Ed., and the MLA Style Manual, 2nd Ed..
MLA
"Sabbath day's journey." In A Dictionary of the Bible. Ed. W. R. F. Browning. Oxford Biblical Studies Online. May 22, 2013. <http://www.oxfordbiblicalcstudies.com/article/opr/t94/e2168>.
Chicago
"Sabbath day's journey." In A Dictionary of the Bible. , edited by W. R. F. Browning. Oxford Biblical Studies Online, http://www.oxfordbiblicalcstudies.com/article/opr/t94/e2168 (accessed May 22, 2013).