Genesis 36 contains an important tribal reference that appears elsewhere in Scripture: Amalek. We learn from chapter 36:12 and 16 that Amalek was a son of Eliphaz, Esau's firstborn. But verse 12 tells us that he was unique from Eliphaz's other children; his mother was Timna, a concubine. Despite this ignominy, Timna became a powerful regional tribe and a terrible foe of Israel.
Unlike the rest of the Edomites, Numbers 13:29 states that they lived in the Negev, the semidesert region of modern southern Israel. When Israel traveled toward Canaan, the Amalekites went out to attack Israel without cause at Rephidim in the Sinai (Exodus 17:8-13). Again, they attacked them at Hormah, near Beersheba, in Numbers 14:45.
In Deuteronomy 25:17-19, God condemns the Amalekites for their hostility, "he met you along the way and attacked among you all the stragglers at your rear, but you were faint and weary, and he did not fear God." Not content with two acts of unprovoked aggression, the Amalekites attacked Israel again in Judges 3:13 and Judges 6:3. Consequently, God commanded Israel to utterly annihilate Amalek after they defeated their other enemies in Israel.
That time comes with the advent of Israel's first king, Saul. God told him, "Now go and strike Amalek and devote to destruction all that he has, and do not spare him; but put to death both man and woman, infant and nursing baby, ox and sheep, camel and donkey.’” (1 Samuel 15:3) Sadly, chapter 15 records that Saul only killed most of the Amalekites, saving some livestock and the king of the Amalekites, King Agag.
After this, Samuel went to Saul, condemned him for his compromise of God's command, and killed Agag "And Samuel hacked Agag to pieces before Yahweh at Gilgal." (1 Samuel 15:33)
Even after these attacks, we learn that other Amalekites had escaped and regrouped to attack Ziklag in Judah, and take captives (1 Chronicles 4:42-43). King David and his men responded quickly, rescued the captives, and defeated the Amalekites again, but 400 escaped on camels!
Later, in 1 Chronicles, we read that Hezekiah found more Amalekites who were staying in Seir and killed them (1 Chronicles 4:42–43).
But it seems like, as much as Israel's kings try, they can never eliminate this brutal and persistent tribe. Many years later, in the 5th century, the book of Esther tells us that one Amalekite descendant of King Agag lived on in Persia. The Persian Empire was the world power. And Haman, an Agagite, hatched a scheme to take final vengeance and kill all Jews in Esther 3.
Only God's grace working through two faithful Jews, Mordecai and Esther, lead to the Gentile king Ahasuerus, killing him. After that we hear nothing more of Amalekites.
What do we learn from this record of the worst of the Edomite tribes? Don't compromise on God's command. The command to kill all the Amalekites seemed harsh to Saul. He didn't want to kill another national leader like himself. Little did he know at the time, if all the Amalekites weren't killed, they would survive and try to kill all the Jews almost 600 years later.
Sometimes God's word might seem harsh to us. We might want to compromise on our obedience. But He is more loving and more wise than we are. The lesson of the Amalekites is that God's people need to guard and obey his word without compromise, trusting that He knows better than we do.