Did you ever think of your mind as a farm or even a garden? God considers it one! In Jer. 4:3b, the Lord says to "Break up your unploughed ground and do not sow among thorns." when one considers the verses around v. 3, it is not hard to imagine that He is referring to something spiritual.
V. 1: "[P]ut your detestable idols out of my sight and no longer go astray."
V. 4: "Circumcise your hearts."
It struck me that perhaps in v. 3b God is referring to our minds (or our minds/hearts). The thorns referred to may be a reference to temptations or (considering the context of this passage) sin itself. The "unploughed ground" could be a hardened heart or a neglected part of our being. A part that has soaked up the good teachings of our parents, but has yet to be used to it's potential. The Lord seems to be saying, "Leave behind things of the past--this field of thorny sins. You are making no progress by plowing these thorns. You cannot overcome them for they are stronger than you.
"Instead," He counters, "Plow up new soil in your heart and mind. Take these seeds of hope I have given you and plant them min untouched, unadulterated soil. Or--even better--plant them in nourished and cultivated soil that has been prepared by good training."
This is quite liberating because it breaks the cycle of temptation so many fall into. The tenet is simple--do not stay in a place of temptation (physically, emotionally, spiritually or mentally) because, if you do, you will find yourself sinning again. Instead, leave that field of thorns, cut the evil from around your heart (circumcision of the heart) and plow up those fields within you that God is desiring to use.
