The 1st baby that was born, his skin colour was a bit red. He also had hair all over his body, like an animal skin. Isaac and Rebekah named that baby Esau.
Then I will give you that food to take to your father. He can’t see, so he will think that you are Esau, and he will do that ceremony with you before he dies. He will ask God to be good to you as the next leader for our family.”
So Isaac didn’t know that Jacob tricked him. He thought, “Now I know that this is Esau, because his arms are really hairy. I will eat that food that he made, and then I will ask God to be good to him as the next leader for our family.”