This is how Jeremiah describes those who trust in mankind. A man who makes flesh his strength. A man who turns from the LORD.
There is an austere beauty in the Arizona desert, in the forests of cacti. It is not like the deserts of the Bible: deserted places without bushes, or even weeds, to give beauty. The eye seeks and finds only dirt, stones, and barren hills. A wasteland. So is the man who trusts in human flesh. Whether I look for satisfaction in government, in the influence of men, in family, a friend, or my husband, all are sure to leave me empty. Or if I place my confidence in self, my heart would be a land of salt.
In ancient times after the victorious army sacked a city, tore down the walls, and burned the houses, as the final insult they would sow the ground with salt. Ground, sown with salt, cannot sustain crops. In the days before refrigerated trucking, to sow the fields around a city with salt was the final death blow (at least in theory, in actuality it didn't always work). If a city could not grow food, it could not rebuild; their name and memory could be extinguished. Think of the Dead Sea, nothing survives there.
In chapter 17:7-8 Jeremiah goes on describe the man who trusts in the LORD, whose trust is the LORD, using words echoing Psalm 1.
He will be like a tree planted by the water,
That extends its roots by a stream
And will not fear when the heat comes;
But its leaves will be green,
And it will not be anxious in a year of drought
Nor cease to yield fruit.
Trust in the LORD is the way out of the desert. The LORD plants us, that He may be glorified, by streams of living water. Living water draws down our roots, and trees with deep roots are drought tolerant trees. Though the summer should be hot and dry, though the rain doesn't fall from heaven, though it is a time of fear, the planting of the Lord is green and bears fruit.
I have left behind the desert wastes. He has transplanted my heart from dry, rocky soil and set me down beside streams of life. I pray the conquering King would go back and sow salt in the soil of my flesh. Tear down the walls of self-confidence and leave an uninhabitable wasteland, so that my hope, my confidence, my joy and my satisfaction, are in the Lord Jesus Christ. In Him alone.