According to Mt. 5:17-19 our standard for behavior is the “Law of Moses.” (Think of the 10 Commandments given in the OT and ways for obeying them. This, of course, was not to earn salvation–which is given by the grace of God–but to show people how to live.)
Now Jesus in one of His sermons, spells this out. Here’s His list¹ of things that are wrong:
(1) evil thoughts
(6) deeds of coveting and wickedness
For more use the DOOR.
People who love God crave to know what’s right and what’s wrong. What standards has God provided for us? In one way that’s pretty clear. God gave believers the Old Testament Law, which He clearly said (in Mt. 5:17-19) is the standard to go by. Two quick comments about this: Certain particular laws (or rules) to consider are things directly connected with Temple service and regional and historical time limitations are impossible to follow. For example, now there is no Temple, and geo-political expansion of the world of believers and technological advancement is radically different from way back then².
The other thing is that these items are almost all expressed in general terms. That’s even true with the 10 Commandments. Human nature desires creating a “check-off list” so we can identify points that we can aim at and accomplish (often so we can go about what we really want to do).
The quest of Christian living then (or it certainly seems to me) is to–through prayer, meditation, and daily observation–identify how to specifically obey God and, for example, deciding how “evil thoughts,” “envy,” or “slander” can be avoided day by day.
Not an easy job.
But think of the the poor person who has no basic guideline to go by–and uses his “pride” (see above) without checks and balances to go about daily living–without even considering first-order responsibilities: loving God, in whose image one is created, with all one’s heart, mind, soul, and strength.
¹ Not a full list, certainly, but one that gives a person a start on what to think about. Further, the English translation used here is the New American Standard Bible.
² This, of course, raises a lot of questions (fortunately) out of bounds for a quick adozenseconds conversation…