Q. When reading the commandments, how do you know which apply today and which ones don’t?

A. When reading and studying anything in the Scriptures, there are certain rules to go by. A simple set of rules that will help are called the “7 Rules of Hillel” and they are quite common and have been used for several thousand years. These rules existed long before Hillel. He lived in the 1st century along with another man called Shammai. They were leading figures in 1st century Judaism and both were heads of “schools’ named after them. Hillel’s grandson was Gamaliel, who taught Paul. These rules of interpretation can be found in Paul’s writings and was possibly what he was referring to in 2 Tim 2.15. I’m going to list them briefly here but further research can be done on your own.
1) Light to heavy: If A is true B, then how much more is C
2) equivalence of expressions: An analogy is made between two separate verses on the basis of similar words being used
3) Building a father (truth) from one verse: One very clear verse is the foundation for a rule for all other similar cases
4) Building a father from two or more texts: two verses or truths serve as a foundation for a conclusion
5) general and the particular: a general statement is made and is followed by a single statement which itemizes a particular rule. For instance Genesis one generalizes, Genesis 2 particularizes.
6) An analogy made from other verses: Two verses may conflict, so a third is brought in that solves the conflict
7) explanation obtained from the context. The total context in which the verse or passage is found has to be considered in order to get the proper meaning.
Now, how do you apply these to what commandments apply today. Let’s take sacrifices for instance. Do they apply today? The answer would be no because there is no Temple or priesthood. They can only be offered in the place where God chooses to put His name. At this point it is Mt. Moriah in Jerusalem and only when there is a functioning priesthood and Temple, in particular the Altar. However, just because a commandment cannot be done doesn’t mean we shouldn’t study them and find out what the meanings are. The biblical festivals cannot be kept exactly either because they involved Temple worship and sacrifices. You see, Yeshua’s death has nothing to do with whether or not sacrifices are offered, it has to do with the Temple, Altar and priesthood. Paul and the 1st century believers offered animal sacrifices 30 years after Yeshua’s death (Acts 21). Tithing is another commandment that is not valid today for many of the same reasons. Tithing was done only if you lived in the land, made a living in agriculture and the tithe was given to the Levites and they distributed it to the priests, and the needy. I think it’s funny how false teachers will tell you that the Law is done away with then tell you to tithe, and people fall for it because they don’t understand how to interpret the Scriptures. On the contrary, eating a biblically kosher diet does apply everywhere and you don’t have to have a functioning priesthood or Temple to avoid pork. The commandment to not murder, lie, commit adultery, not cheating your neighbor applies everywhere. You just have to ask yourself “how can I keep this commandment” and implement it into my life and go as far as you can. So, here is what I would do in order to understand what to do. Find yourself a good, balanced Torah teacher who you can interact with. You’ll learn more and a lot faster than doing it by yourself. Remember you can only rise to level of whoever is teaching you. If you find a teacher who knows much, you will learn much. Secondly use the 7 laws of Hillel, in particular number 7 which deals with context. Study the verses over and over again, it takes a lifetime. Read commentaries about the verse or commandment being studied. Ask yourself if it’s possible to keep this today in light of living outside the land, no Temple, priesthood and other applications. You need to find some group of like-minded believers who can help you study and understand the scriptures. Start there and see where the Lord leads you.