Please explain Galatians 2:21, 3:13

Galatians was the Apostle Paul’s letter to a group of churches in Asia Minor. These churches were composed of Christians who were originally heathen or converted Jews. Some of these believers had the correct understanding of the efficacy of Jesus’ sacrifice to cover our sins, but were now being told that in order to find acceptance by God they were required to keep the Law of Moses and observe its ritual of circumcision. Paul’s letter was written to address this error.

When Paul gets to Galatians 2:21 he is concluding his argument that what the Law held out to Jews was justification in God’s sight, and therefore a right to everlasting life, but it could not be attained because none were perfect, and anything short of that was unacceptable to God.

Paul concludes by saying that he does not disesteem or reject the grace of God in giving the Law to the nation of Israel. It was a benefit in many ways. But he concludes that if righteousness could be attained by keeping the Law, then there was no need for Jesus to die.

Galatians 3:13 Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is every one that hangeth on a tree:

When Adam sinned, God’s sentence was pronounced against him, and the curse of death was carried out upon him 930 years later. It continues upon his posterity to this day. But the curse referred to by Paul here is an additional curse upon the nation of Israel as a result of their failure to live up to the Law Covenant that had entered into with God at Sinai. In order to redeem the Jews it was necessary for Jesus to die by crucifixion (hanging on a tree and thus bearing the curse) to take the place of those who publicly proclaimed that they would keep God’s law and thereby to lift the curse of the Law upon them.

What is the full meaning of Shem, the son Noah?

Shem is one the three sons of Noah as recorded in Genesis 5:32 and 6:10, “And Noah was five hundred years old: and Noah begat Shem, Ham, and Japheth.”  His name means “Name” or “Renown” (Fame).  Shem was probably the firstborn sonof Noah since he is mentioned first. Additionally, the words "brother of Japheth the elder" in Genesis10:21 are more correctly rendered "the elder brother of Japheth," as in the Revised Version of the Bible.

Shem was one of the eight people who were spared from the flood (Genesis 7:13).  He was apparently a faithful servant of Jehovah God because Genesis 9:26 and 27 teach that God is the “Lord God of Shem.” In addition, it was from Shem’s children that the nation of Israel came into being.  Genesis 11:10-26 and 1 Chronicles 1:24-27 list Shem’s descendants which culminate with Abraham, Isaac and Jacob.

Some speculate that Shem may have been the priest and king Melchisedek in Genesis 14 and Psalms 75:3. Shem’s longevity indicates that he would have been alive at the time of Abraham, but there is no direct scriptural proof that these two great people are one and the same.  Others say that Shem may have been the architect of the Great Pyramid of Giza. Again, we have no definitive proof of this clam; although, it too presents some interesting ideas.

The chief significance of Shem is that he is mentioned in the lineage of Jesus in Luke 3:36. “Which was the son of Cainan, which was the son of Arphaxad, which was the son of Sem, which was the son of Noe…” Sem is the Greek version of the name Shem and Noe the Greek version of the name Noah.