On many occasions, but most memorably in his great "I Have a Dream" speech in Washington, D.C., and in his final speech before being killed in Memphis, Martin Luther King Jr. quoted these words from Amos: "But let justice roll on like a river, righteousness like a never-failing stream" (5:24). It's appropriate that Dr. King was drawn to the prophet Amos because, like Amos, Dr. King was called to be a prophet for justice.

As far as we know, Amos was a humble man who earned a living by keeping a flock near Tekoa, close to Bethlehem. He lived during a time of great economic prosperity for Israel, but that wealth was not shared by all. It was also a time in which the rich grew richer and the poor grew poorer.

In chapter four, Amos begins his indictment, addressing some of the rich women of Israel as the "cows of Bashan." He cries out against them for oppressing the poor and crushing the needy, while they say to their husbands, "Bring us some drinks" (4:1).

Amos then spreads the indictment to all of Israelite society for refusing to uphold justice in the courts (5:10), levying an unfair "straw tax" and grain tax on the poor (5:11), and oppressing the innocent and taking bribes (5:12).

But even as the Israelites were perpetrating this economic oppression, they maintained an outer religiosity. They faithfully went to the temple for worship, offered the proper sacrifices, and maintained all the religious festivals. In other words, they observed all the proper religious practices but didn't care about the justice that God demanded in his law.

That brings up Amos's most famous sermon, in which he speaks for God against the injustices of Israel. "I hate, I despise your religious festivals; your assemblies are a stench to me. . . . But let justice roll on like a river, righteousness like a never-failing stream" (5:21-24). Justice is more important to God than any of our religious practices. It is the cornerstone of God's law.

It's easy to see why Martin Luther King Jr. was drawn to Amos. He too lived in a land of gross injustice in which his fellow African Americans were mistreated, relegated to second-class citizenship, oppressed, and discriminated against. And this injustice was tolerated, even practiced, by people who called themselves Christians and went to church every Sunday.

Here's how Dr. King expressed it in a speech he gave to inspire people to continue the famous Montgomery, Alabama, bus boycott:

My friends, I want it to be known that we're going to work with grim and firm determination to gain justice on the buses in this city. And we are not wrong, we are not wrong in what we are doing. If we are wrong, then the Supreme Court of this nation is wrong. If we are wrong, the Constitution of the United States is wrong. If we are wrong, God Almighty is wrong. If we are wrong, Jesus of Nazareth was merely a Utopian dreamer and never came down to earth. If we are wrong, justice is a lie. And we are determined here in Montgomery to work and fight until justice runs down like water and righteousness like a mighty stream.

Through Dr. Martin Luther King Jr., like the biblical prophets before him, God spoke to a whole society about the justice that's the foundation of his law and his truth.