I also wonder how many pastors who are paid for their work, certainly a biblical principle, rely on verses such as 1 Tim 5:17-18 for their wages. But this verse is using the OT ( Deut 25:4 ) as a proof that elders can be compensated. Obviously Paul saw that a correct use of the OT law was applicable to the NT believer.
How often do people use 2 Tim 3:16-17 to speak of the inspiration of scripture and then in effect discard the OT law. This passage in context speaks to the OT and while it obviously applies to the NT as well the original audience would have heard that the OT “was breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be competent, equipped for every good work.” If we are to follow the words of God, through Paul, we are then to use the OT law as it was intended.
In saying this there is work to be done to understand the principles of the OT law as we do not blindly and woodenly follow them and go and build a parapet on our roof (Deut 22:8). I am also not saying that the ceremonial law is still in effect as it has been fulfilled by Christ who it pointed to. I would also say that while most tend to see the other laws as either moral or civil, in truth they are both moral as the civil laws are an outworking of the ten commandments, the moral law. So I would say we are still left with the moral law as seen in the 10 commandments and the civil codes. Of course we are to discern the biblical principles so as to apply them to all of life. An example is the parapet law found in Deut 22:8 where the principle is a call to responsibility for ones property and not necessarily for building a railing on ones roof, that is unless one has a roof people meet on. Some laws may be easier to discern then others but in the end that does not negate our call to follow them as worship of God.
I realize that for some to hear that we are to follow all of God’s laws, both OT and NT, is legalism. I would say that if one does not seek to follow God’s plan for all of life as seen in “ALL” of His word then you are left with devising your own laws and that is truly legalism. Keep in mind that Jesus did not need to repeat all the OT commands in the NT as they are assumed as valid unless He explicitly negates them, as with the ceremonial laws. Even in Mat 22:36-40 Jesus affirms the OT law as when He is asked about the greatest commandment He does not pick one but summarizes them into those that deal with our relationship with God (Commandments 1-4) and our relationship with man (Commandments 5-10) and in V40 makes sure we do not miss the connection with the OT by reminding us that these two undergird the OT law.
We as a people of God that proclaim to believe in the inerrancy of scripture and the sufficiency of scripture need to live as such. We need to seek to truly live as if God’s word is sufficient and if one does not use the OT and only seeks out the NT for guidance then scripture will not be sufficient. We need all of His word for it to be sufficient and we need to regain this understanding of scripture as sufficient for all of life.