The first stanza of the poem focuses on singing and music. The speakers of the poem say that we should all lift our voices and sing together like one big happy family in honor of liberty. The song that the speakers call on us to sing is full of hope and faith.
The second stanza digs into the very difficult history of African-Americans. The speakers refer to the "stony" road that African-Americans have walked and the "rod" that was used to "chast[en]" them. The stony road and the rod are both metaphors that suggest the violence and difficulty of the African-American experience. Even so, the speakers call on us listeners to continue to have hope. They say that African-Americans have come a long way, through a lot of hardship, and now they're standing at the brink of a new, more hopeful future. Hurray!
The final stanza of the poem focuses on God. The speakers acknowledge that, if they've come this far, it's because of the Big Boss sitting up there in the clouds: God. It's God who has guided the speakers through difficult paths, and the speakers ask God to continue to guide them. The poem ends with the speakers hoping that they will "forever" be true to their God and to their native land (America).