The first documentation of slavery was in the Bible. It comes from the story of Joseph, a Black man who was sold as a child by his brothers to some Ishmaelite people traveling to Egypt.
Joseph brothers cast him into a pit out of anger because he was his father Jacob favorite son. His brothers disliked him for telling them that the sun, moon and the eleven stars made obeisance to him. Joseph was referring to his Mom and Dad and his 11 brothers.
“And Judah said unto his brethren, what profit is it if we slay our brother, and conceal his blood. Come, and let us sell him to the Ishmaelite (Arabs) and let not our hand be upon him; for he is our brother and our flesh. And his brothers were content. Then there passed by Midianites merchant-men; and they drew and lifted up Joseph out of the pit, and sold Joseph to the Ishmaelite for twenty pieces of silver: and they brought Joseph into Egypt.” (Genesis 37:26-28)
God was behind all of this; he used Joseph as a tool to preserved Israel. He sent one Israelite to Egypt as a slave to save a nation. This is a long time before the slave trade act you heard of in History class.