New Defender's Study Bible Notes
5:14 set on a hill. Christ very likely was thinking of the six cities of refuge provided in Israel (Numbers 35:15), all of which were cities set on a hill, so that they could be seen for miles around, thus expediting their sighting by anyone seeking refuge in them (see also Joshua 20:7-8). They could be seen even at night by their watchfires. In a sense, believers should also be lights in a dark world.