Deuteronomy 15:9Take care lest there be an unworthy thought in your heart and you say, ‘The seventh year, the year of release is near,’ and your eye look grudgingly on your poor brother, and you give him nothing, and he cry to the Lord against you, and you be guilty of sin.
During the summer months I get a lot of time to spend with my kids.  But a lot of that is teaching them how to being around each other for long periods of time.  So they’ll say or do something to one another, that makes we wonder if siblings are supposed to like each other!
In an attempt to mitigate at least some of the issues, I ask them individually, “what is the problem?”  Every time it always starts with a negative thought towards their sibling, that turns into “their truth”, and they act on the truth they thought towards the other.  Of course being young kids, they don’t analyze whether that thought is justified or not, they just feel that way, and act on it as if it is right!
This is why renewing our mind to the truth is much like exercise training.  Being built up enough in the truth, that we “reflexively” analyze the way we should think. Compared to allowing thoughts to come in, that we don’t analyze with the truth, and act on unworthy thoughts. This passage is in context of how God wanted His people to treat each other during the Sabbath year.  To have “guard rails” against thoughts He knew people would have when it came time to pay back their brothers…
It’s easy to have thoughts towards a person that you shouldn’t have, but the test is whether you seek out the truth of those thoughts, or let them rule your heart and interaction with others?  The enemy knows how delicate our mind can be when unguarded by truth, but do you?(Ephesians 6:16)  All kinds of negativity and wickedness takes place first in an “unworthy thought” that goes unchecked…
In His Love, Ld