Beware of the Judiazers. The Apostle Paul continually warned church about slipping into a “gospel” that was other than they had originally received. He pulled no punches in describing those who wanted to add the yoke of the law the gospel of grace. I can imagine that those who were teaching the error were fully convinced their doctrine was correct. After all, how could someone be sanctified if they weren’t circumcised, and they ate pork, and didn’t attend the festivals or tithe, and so on? Weren’t all those things in the scriptures? Didn’t Paul tell Timothy “All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness”?
Yes, those things are in the scriptures, but care must be taken in considering who they were speaking to and in what context. Paul goes to great lengths in the books of Romans, Galatians, and Hebrews, with honorable mentions in the books of Timothy, Ephesians, and his other letters, to explain that in Christ we are under a new covenant:
[8:1] Now the point in what we are saying is this: we have such a high priest, one who is seated at the right hand of the throne of the Majesty in heaven,  a minister in the holy places, in the true tent that the Lord set up, not man.  For every high priest is appointed to offer gifts and sacrifices; thus it is necessary for this priest also to have something to offer.  Now if he were on earth, he would not be a priest at all, since there are priests who offer gifts according to the law.  They serve a copy and shadow of the heavenly things. For when Moses was about to erect the tent, he was instructed by God, saying, “See that you make everything according to the pattern that was shown you on the mountain.”  But as it is, Christ has obtained a ministry that is as much more excellent than the old as the covenant he mediates is better, since it is enacted on better promises.  For if that first covenant had been faultless, there would have been no occasion to look for a second.
 For he finds fault with them when he says:
“Behold, the days are coming, declares the Lord,
when I will establish a new covenant with the house of Israel
and with the house of Judah,
 not like the covenant that I made with their fathers
on the day when I took them by the hand to bring them out of the land of Egypt.
For they did not continue in my covenant,
and so I showed no concern for them, declares the Lord.
 For this is the covenant that I will make with the house of Israel
after those days, declares the Lord:
I will put my laws into their minds,
and write them on their hearts,
and I will be their God,
and they shall be my people.
 And they shall not teach, each one his neighbor
and each one his brother, saying, ‘Know the Lord,’
for they shall all know me,
from the least of them to the greatest.
 For I will be merciful toward their iniquities,
and I will remember their sins no more.”
 In speaking of a new covenant, he makes the first one obsolete. And what is becoming obsolete and growing old is ready to vanish away.
(Hebrews 8:1-13 ESV)
You can use the search tool on www.biblestudytools.com to look up the many other references to the new covenant.
I would recommend the reading of the entire books of Romans, Galatians and Hebrews, often and intently, to get a grasp of the new covenant, and why Paul was so adamant that the Judiazers not be given place.
Why am I bringing up this topic today, in an age where it seems that God’s grace has been cheapened to be interpreted as “anything goes”? Because Paul, through the Holy Spirit, deemed it to be deadly to the faith. And because it is sneaking back into our church doctrine and teaching in a very surreptitious way.
My observation for the reasons for this reappearance of the Judiazers is 1) it is a misguided response to the apparent licentiousness of the modern church (although that licentiousness does need addressing), and 2) in standing in concert with Israel, many believers have obfuscated the division between the Old Covenant and the New Covenant, wanting to interpret the old covenant law as continuing to apply to those under the new covenant. This second instance is directly in line with the form of Judiazer doctrine that Paul so vehemently fought against.
So, after reading Romans, Galatians and Hebrews, (I am intentionally not referencing specific verses because the entire books address the issue, and you really, really should read the whole thing) you can see that we are not, as in the example Paul uses in Romans 7:1-6, married to the law (the old covenant).
Or do you not know, brothers—for I am speaking to those who know the law—that the law is binding on a person only as long as he lives? For a married woman is bound by law to her husband while he lives, but if her husband dies she is released from the law of marriage. Accordingly, she will be called an adulteress if she lives with another man while her husband is alive. But if her husband dies, she is free from that law, and if she marries another man she is not an adulteress.
Likewise, my brothers, you also have died to the law through the body of Christ, so that you may belong to another, to him who has been raised from the dead, in order that we may bear fruit for God. For while we were living in the flesh, our sinful passions, aroused by the law, were at work kin our members to bear fruit for death. But now we are released from the law, having died to that which held us captive, so that we serve in the new way of the Spirit and not in the old way of the written code.
We are not tied to the old covenant law. In Jesus, we have been given a new commandment:
When he had gone out, Jesus said, “Now is the Son of Man glorified, and God is glorified in him. 32 If God is glorified in him, God will also glorify him in himself, and glorify him at once. 33 Little children, yet a little while I am with you. You will seek me, and just as I said to the Jews, so now I also say to you, ‘Where I am going you cannot come.’ 34 A new commandment I give to you, that you love one another: just as I have loved you, you also are to love one another. 35 By this all people will know that you are my disciples, if you have love for one another.