Salt is essential to human life; it is so important, that we were designed with specific salt-receptors on our tongues.  If we do not have enough salt, we will seek out salty food, because without it we will die.  Salt is also important to flavour our foods (Job 6:6); but more significantly, in large quantities it will kill bacteria and so it has been used as a food preservative for thousands of years.  Likewise, it is an excellent disinfectant for wounds, and sanitizer of human and animal waste.  Indeed, it is so useful that salted manure will safely put essential nutrients into soil to increase the crop yield.  Salt was so important that part of a Roman soldier’s pay was in salt – his ‘salarium’ (from the Latin, meaning ‘salt-money’ or our modern-day ‘salary’).

The Dead Sea was Israel's prime source of salt.  The mineral nutrients, which were washed out of the ground as the Jordan River made its way south, were precipitated as the water evaporated in the earth’s lowest place.  But after collecting the salt crystals, with other minerals, in the salt pans, it had to be transported for sale.  If, during that process, the rains came and washed the salt out of the mineral load, it would be of no value for flavouring or preserving food, as a disinfectant or fertiliser.  Once the salt had been washed out, there was no way to make it potent again; it was best used to fill holes in dirt-track roads.

Jesus used the example of salt to explain that discipleship was not a game.  If the characteristics of the life of Christ, thought-through and willing self-sacrifice, were not rooted in His followers, those people would be useless in His service. Admiring Jesus, enjoying the company of His people, listening to His Word and professing to be a disciple are all meaningless without a determined commitment to obey Him in sacrificial service (Matthew 7:24-27).

The analogy is very simple and yet profound.  Of course, some do not want to hear that message, but those who are serious about pleasing Jesus will accept the challenge, and guard the potency of their spiritual lives (1 Timothy 4:13-16). Christian commitment is the product of God's implanted loving power and our disciplined submission to Him, through thoughtful planning and sacrificial obedience.  That will glorify Jesus, keep us pure and help purify the world.  It is the essential challenge for 'modern' believers too: we must all take the challenge seriously today!