In the Greek this pronoun is emphatic: “Ye are the light of the world.”

 Light has ever been a symbol of the divine presence (see on Gen. 1:3; 3:24). John refers to Jesus as “the light of men” shining forth amid the darkness of this world (ch. 1:4-9). Toward the close of His ministry Jesus referred to Himself as “the light of the world” (see on John 8:12; 9:5). Having accepted Jesus as the light of the world, a Christian, if true to his calling, becomes a reflector of that light. In Messianic prophecy Jesus is referred to as “a great light” (Isa. 9:2), and as the “Sun of righteousness” (Mal. 4:2; see on Luke 1:79). When the true Light illumines men, they are admonished to “arise, shine” (Isa. 60:1-3). Those who love and serve the Lord are pictured as being like the “sun” (see on Judges 5:31), both here and in the hereafter (see Matt. 13:43). It was yet morning as Christ spoke (MB 38), and the sun was ascending the heavens toward the zenith (cf. Ps. 19:4-6). In a similar way the Twelve—and all future citizens of the kingdom as well—were to go forth and let their light shine abroad in the world, dispelling the darkness of sin and ignorance of the will and ways of God. See on John 1:4, 7, 9.

Ancient Palestinian cities were commonly situated on hills, as their ruins testify today. Such a city would be visible from a considerable distance. From the place where Christ and the multitude sat, many towns and villages were visible on the surrounding hills (MB 39).

 Gr. kosmos (see on ch. 4:8).