There is an old error; not exactly eronious; but an old error; it's the one that tried to lift it's head during the first century church, when it raised a big uproar among the Apostles till they all had to meet at the council in Jerusalem to deal with this matter (Acts15) this error is seemingly back with with a vengeance and that error is mixing the Law of Moses with the Grace of Jesus Christ. Jesus said in Matt.5:17 "I am not come to destroy the Law but to fulfill"Jesus fulfilled the law by meetings its just demands by a sinless life and thereby satifying its curse by dying on the cross and ultimately declaring a New and Living way by the resurrection from the dead. Jesus said in Matt.9:17 "Neither do men put new wine in old bottles or else the bottles break and the wine runs out..."). This is reverting back to the Law which is nothing more than what the word of God declears as to "Frustrate the Grace" (Gal.2:21), As in Peter"The dog is turned back to his own vomit" (Prov. 26:11, 2Pet.2:22). Being that it is by the Grace of God that we are saved; ie Eph.2:8 this Grace should be the first thing we come to know and understanding before anything else."This error is usally caused by "Not rightly dividing the word of truth" (2Tim.2:15). This mixing of Law and Grace is nothing other than a brewing pot for Legalism. Which is one of the most dangerous kinds of teachings one can ever have in a church. "A little leaven leavens the whole lump" (Gal.5:9), in other words a small amount of false doctrine will ultimately consume the whole truth. Here's a quick outline of Law and Grace.

Sadly many Christians today are living under the pretence of the law not rightly understanding the substitution and identification of them in Christ and Christ in them through the reckoning and power of the Holy Spirit. The Word of God makes a clear distinction between Law and Grace, putting  the Law in one dispensation and Grace in another. The Law was given by (through) Moses but Grace and truth by (through) Jesus Christ. John.1:17, by the Law we are to understand the "Mosaic Law" was given to Moses by God on Mount Sinai. It was threefold.

1. The Moral Law Ex.20:2-17

2. The Civil Law Ex. 21:1-24:18

3. The ceremonial Law Ex. 25:1-40:38

                         The Law

The "Law" was not given to Justify men, for by the deeds of the law shall mo flesh be justified. Rom.3:20, Gal.2:16. The Law was given so men might know what sin is, for the Law is the knowledge of sin, men would not have known that covetousness was sin if the Law had not said "Thou shalt not covet" Rom.7:7. The Law was given to stop men's mouths and to stop men from boasting in their own Righteousness and to see themselves guilty before God. Rom.3:19. The Law was given as a schoolmaster to lead men to Christ. Gal.3:24-25. All of the rites and ceremonies pointed to Christ. Now that Christ has come neither Jew or Gentile is under the Mosaic Law, for Christ fulfilled the law by meetings its just demands. Christ then is the End of the Law for Righteousness to everyone who believes. Rom.10:4. Therefore believer's are dead to the Law. Rom.7:4, that is believer's is no longer under the bondage of Legalism But now under Grace.

                               Grace

"By Grace are you saved through faith and that not of yourselves it is the gift of God not of works lest any man should boast. Eph.2:8-9

But God Commended His love towards us in that while we were yet sinners Christ died for us. Rom.5:8. (Jesus did the work for us this is the pinnacle of all grace, He being our substitute, we being identified in Him. This is marvelously Amazing!

We see then that Grace is a gift. if a man receives salvation by his works or efforts it's no longer a gift but a reward. Grace is not something given to us to help us keep the Law. Grace is undeserved or unmerited favor. The Love of God is the source of Grace. (ie Jn3:16). The channel of Grace is Christ "Grace and truth came by Jesus Christ" Jn.1:17, Titus 2:11.