Why did quakers eventually oppose african slavery? how was it opposed to their religious principles?

This change happened gradually. Quakers were some of the first people in the Americas to own slaves. However, objections were brought up by Dutch Quakers in the 18th century that changed the Christian sect's outlook on owning slaves. From these objections, Quakers gradually stopped owning slaves and became some of the most vocal abolitionists. The Quaker biblical justification was in the verse Matthew 7:12 which stated that Christians had a responsibility to adhere to a higher standard of living morally. The Quakers did not believe owning slaves was a part of living up to these standards.