The Holiness movement is a Christian movement that emerged chiefly within 19th-century Methodism, and to a lesser extent influenced other traditions such as Quakerism, Anabaptism, and Restorationism. The movement is historically distinguished by its emphasis on the doctrine of a second work of grace, which is called entire sanctification or Christian perfection. Churches aligned with the holiness movement additionally teach that the Christian life should be free of sin. For the Holiness movement, "the term 'perfection' signifies completeness of Christian character; its freedom from all sin, and possession of all the graces of the Spirit, complete in kind." A number of evangelical Christian denominations, parachurch organizations, and movements emphasize those beliefs as central doctrine.

Quakers are people who belong to the Religious Society of Friends, a historically Protestant Christian set of denominations. Members of these movements are generally united by a belief in each human's ability to experience the light within or "answering that of God in every one". Some profess a priesthood of all believers inspired by the First Epistle of Peter. They include those with evangelical, holiness, liberal, and traditional Quaker understandings of Christianity. There are also Nontheist Quakers, whose spiritual practice does not rely on the existence of God. To differing extents, the Friends avoid creeds and hierarchical structures. In 2017, there were an estimated 377,557 adult Quakers, 49% of them in Africa.