Please answer a question about the following article about North Carolina:

Besides slaves, there were a number of free people of color in the state. Most were descended from free African Americans who had migrated along with neighbors from Virginia during the 18th century. The majority were the descendants of unions in the working classes between white women, indentured servants or free, and African men, indentured, slave or free. After the Revolution, Quakers and Mennonites worked to persuade slaveholders to free their slaves. Some were inspired by their efforts and the language of the Revolution to arrange for manumission of their slaves. The number of free people of color rose markedly in the first couple of decades after the Revolution.

After the revolution Quakers and mennonited encouraged slaveholders to do what?
free their slaves