Abraham loved God and believed in him with all his heart. God had a plan to rescue the whole world and Abraham family would play a main part in it. To begin the plan they made a covenant ( a big promise that lasts forever).
God said when you have done my plan you will have more children than stars in the sky. Abraham had always wanted children but he and his wife couldn't have any. He didn't know whether god could give him many children but he chose to trust god and 10 years later they had a son.
In the times Abraham was living in people showed their love to god by sacrificing things to him. A sacrifice is like a gift.
One day, God decided to test Abraham's loyalty but asking him to sacrifice his own son. He didn't want to but he remembered God's covenant and knew you couldn't be father of nation's a have no son so brought Isaac to the hill to be sacrificed.
After Abraham and Isaac had built the altar Abraham, tears spilling from his eyes, told Isaac he was the sacrifice as that was Gods wish. Isaac ,confused, just did what his father said. Abraham raised the knife to kill his son.
Just before the knife hit Isaac God voice echoed on the hill shouting, "stop don't kill the boy let him free". God had only asked Abraham to kill his son to see how loyal he was. Abraham and Isaac embraced harder then anyone had ever done. And Abraham had proved his loyalty to God.