You that are to be my apostles are so eminently, but all you that are my disciples are so also. Christ is the Light of the world Joh_1:4,9; but though the sun be the light of the world, yet it doth not follow that the moon and the stars also are not so: he is the original Light, the great Light who hath light from and in himself. The ministers of the gospel are the lights of the world also; the angels of churches are stars, Rev_1:20, and holy persons are children of light, 1Th_5:5.
A city that is set on an hill cannot be hid. The church is often called the city of God. Christ compares his people here not to a city, but to a city upon a hill; so that all for which our Saviour mentions a city here, is the conspicuity of a city so built. It is as much as if our Saviour should have said, You had need be holy, for your conversation cannot be hid, any more than a city can that is built upon a hill, which is obvious to every eye. All men’s eyes will be upon you.