Jacob got the blessing from Isaac by cheating way

 Genesis 27:1-29

So he went and got them and brought them to his mother, and she prepared some tasty food, just the way his father liked it. Then Rebekah took the best clothes of Esau her older son, which she had in the house, and put them on her younger son Jacob. She also covered his hands and the smooth part of his neck with the goatskins. Then she handed to her son Jacob the tasty food and the bread she had made.

Jacob said to his father, “I am Esau your firstborn. I have done as you told me. Please sit up and eat some of my game, so that you may give me your blessing.”  Isaac asked his son, “How did you find it so quickly, my son?” “The Lord your God gave me success,” he replied.  Then Isaac said to Jacob, “Come near so I can touch you, my son, to know whether you really are my son Esau or not.”  Jacob went close to his father Isaac, who touched him and said, “The voice is the voice of Jacob, but the hands are the hands of Esau.” He did not recognize him, for his hands were hairy like those of his brother Esau; so he proceeded to bless him. “Are you really my son Esau?” he asked. “I am,” he replied.

So he went to him and kissed him. When Isaac caught the smell of his clothes, he blessed him and said,

“Ah, the smell of my son is like the smell of a field that the Lord has blessed. May God give you heaven’s dew and earth’s richness—   an abundance of grain and new wine. May nations serve you
    and peoples bow down to you. Be lord over your brothers,  and may the sons of your mother bow down to you. May those who curse you be cursed  and those who bless you be blessed.”

Why?

Rebekah loves Jacob, so she made a treaty to help Jacob get the blessing of his father, Isaac.

Bless and curse have the same power before the Lord, so be careful to bless and curse anyone else.

Love others better than curse others.

How?

This is the consequence of Jacob and his brother Esau, then it led to a long history of fighting for a few thousand years.