Jamieson, Fausset & Brown

light--emblem of prosperity (Isa 58:10; Job 11:17). health--literally, a long bandage, applied by surgeons to heal a wound (compare Isa 1:6). Hence restoration from all past calamities. go before thee--Thy conformity to the divine covenant acts as a leader, conducting thee to peace and prosperity. glory . . . reward--like the pillar of cloud and fire, the symbol of God's "glory," which went behind Israel, separating them from their Egyptian pursuers (Isa 52:12; Exo 14:19-20).