Avenge O Lord thy slaughtered saints
-- Speaker (Line 1)

Importance: In this first line, the speaker makes it clear the purpose of the poem. It is a form of prayer: a direct address to God (the "Lord" named in this line) to take action to revenge the murdered Waldensians (1). The speaker thus begins with a clear and direct message to God, and to whoever may be reading the poem.

Thy truth so pure of old
-- Speaker (Line 3)

Importance: This line subtly references a complex set of historical beliefs about the Waldensians. Early modern Protestants valorized the Waldensians as having been, essentially, proto-Protestants since ancient times. This served an important political purpose for the Protestant movement, as it allowed them to make a claim that, far from being a new corruption of the ancient Catholic beliefs, they were in fact recovering an even older true church. With these words, Milton echoes this belief, tying the Waldensians' religious practices...