The problem with the people in the days of Isaiah was a failure to live up to the covenant standards of behavior and thus fulfill their putative mission vocation. Of course, in the plan of God, this was all destined from the start. The Exile to Babel was vital to disavow them of their righteousness, exposing the fact that God’s Israel was a blind, deaf, ignorant servant, to purge them of idolatry, immorality and iniquity, and help them see, in the Sovereign Work of God, that the Messiah did all, to bring their pride down low, call them to repent, and experience transformation in the knowledge of the light, in order that they may be salt.

Having lectured on Isaiah recently I’ve come to what I judge is a more satisfying view of the Light of the World & Salt of the Earth passages that commence the Sermon on the Mount.

Traditionally this has been interpreted as the illuminating and purifying effect of the good works of Christians upon the world – either of a conservative or liberal brand.

What has always bothered me about this – though I have preached it myself 3 or 4 times, is that there weren’t really any convincing control as to what we make light & salt mean.

I think having recently started to prepare a lecture series on the 5th Gospel, that the Prophet Isaiah has the answer to what this passage really means.

There are a number of factors we should take into account which all seem to fit and line up:

1. The text in Matthew is written primarily with a Jewish audience in mind.
2. Both light and salt in Isaiah are metaphors for the Covenant in the Old Testament.
3. It is hard to imagine that the City on the Hill, given the fact that Matthew above all draws attention to OT theme fulfillment, is not a reference to Mount Zion.

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