Can someone explain Genesis 12, 21-22?

If you mean Genesis 12:21-22 (ie: chapter 12, verse 21 and 22) -- there is no such thing.

If you mean chapters 12, 21, and 22 --

that is way too massive a question for this forum.

You should come here with more specific questions --

ie: read the chapter yourself, and ask follow up questions here.

But - very briefly --

Chapter 12 starts with the initial covenant between Abraham and God -- or what may be called the Ethnogenesis of the Hebrew clan --

Abraham leaves his family and starts his own clan / nation

and it ends with his visit to Egypt and Pharaoh's attempt to take Abraham's wife for his own harem.

Chapter 21 starts with Sarah conceiving Isaak and goes through a substantial number of important developments in the dynamics of the birth of the Hebrew people and Arab people

And Chapter 22 focuses on teaching the rejection of human sacrifice in the Hebrew religion.

Are you asking about three chapters, 12, 21, 22? I can give you a rundown of Abraham’s life and the promises that God made to him. Abraham was called by God to leave his family and go to the land (what is Israel)…there God promised him that all the land he saw God would give to his descendants forever. God also promised him a son, even though he and Sarah his wife were very old and way past child bearing age. Sarah didn’t believe SHE would conceive so she gave Hagar her maid to Abraham as a wife. Hagar gave birth to Ishmael. God told Abraham that Ishmael was not the promised son, that he and Sarah would have a son. Soon enough Sarah did have Isaac. A few years after Isaac was born, Sarah had Abraham drive Hagar and Ishmael away – there was a lot of fighting and strife between the women and boys. God promised Hagar that Ishmael would also be the father of a great nation (modern day Arab nations). Isaac was a young man when God asked Abraham to sacrifice him. This was a test of Abraham’s faith. If he had enough faith that God would spare Isaac’s life – he figured God would because God said that Isaac was the promised child and through Isaac would Abraham be the father of a mighty nation. Sure enough, God did spare Isaac as Abraham kept the faith and didn’t waiver – went through the proper procedures for sacrificing and was about to kill Isaac. Isaac grew up and married and had twins – Esau and Jacob. Esau’s offspring became the Edomites and Jacobs became the Jewish people.

Yes. It is all about the way God feels about idiots. Further on there is a whole book dedicated to them. Proverbs. My favorite is 26:11. "Like a dog returning to it's vomit, the stupid one keeps repeating his foolishness.: