We were driving through the night in a pickup truck somewhere in the deserts of northwest Mexico. After an evening church gathering, I and several other hermanos were headed home, bumping along in the back as stars pinpricked chilly constellations above us.

The man next to me leaned over. “Pastór,” he asked over the rumble of the truck and the wind’s rush. “What does it take to be a pastor?” He soon made the reason for his question clear. “You see, I am serving as a pastor in my congregation, but there’s just one thing,” he said. “I cannot read.”

The prophet Malachi ministers in the 6th century B.C., the same period in which Ezra is restoring the Law, Nehemiah the walls and Zerubbabel the temple. Malachi speaks into chaos.

Returning to their ancestral land, faith and practices, the people are discovering none of it was quite like their great-grandparents’ dream.

The temple was not nearly so grandiose (Ezra 3:12). The city was insecure (Neh. 2:11-18). The Sabbath went unkept (Neh. 13:15-22). The people had forgotten the Law and the covenant. They could scarcely understand Hebrew (Neh. 8:8).

Malachi addresses the priesthood, corrupted by laxity and desperation, in particular. His underlying question is this: What does it take to be a priest?

The priests were meant to serve God and bless the people, but because they had not taken to heart the holiness required for their role, God says, “I will curse your blessings” (Mal. 2:1).

The priestly covenant was meant to be a covenant of life and well-being, marked by reverence, true instruction and walking/ethics (the word for “walk” in Hebrew, halak, doubles as the word for “ethics”).

“But,” says the Lord of hosts, “you have turned aside from the way; you have caused many to stumble by your instruction; you have corrupted the covenant of Levi” (Mal. 2:8).

As the priests, so the people. God’s purifying fire is kindled against all of them because of their injustice to those on the margins: hired workers, widows, orphans, immigrants — but also because of their dabbling in magic, sexual immorality and swearing falsely (Mal. 3:8).

It all falls in the same ancient and ever-relevant category for God: sin. And it all requires the “refiner’s fire” and “fullers’ soap” (3:2).

There’s one thread of hope: if God’s moral code never changes, neither does God’s mercy. “I the Lord do not change; therefore you . . . have not perished” (3:6).

Instead, says God, “return to me, and I will return to you” (3:7). Then you will be happy, will be God’s special possession, will see the difference between the righteous and the wicked (3:12, 17-18).

It’s God’s command in the ancient Torah all over again: “Be holy, for I the Lord your God am holy” (Lev. 19:1).

Micah makes his own call to holiness in a much earlier era —the days of the 8th-century B.C. Judean kings Jotham, Ahaz and Hezekiah. The Assyrian empire is ascendant, soon to destroy Israel to the north.

Though Judea will be miraculously spared (see Isaiah 37), Babylon — says the prophet — will later plow Jerusalem like a field and turn the city into an overgrown rock heap (Micah 3:12).

Again the rulers have pioneered the way in the vampiric injustice of sin: “You hate the good and love the evil, [you] tear the skin off my people, and the flesh off their bones” (3:2).

Micah, from small-town Moresheth, brings his challenge to the intellectual and cultural heart of Jerusalem, speaking because he is “filled with power, with the spirit of the Lord and with justice and might” (Micah 3:8).

His message, wanky to the lettered elites, is the same old shofar call to holiness. The prophet has nothing new to say. God has nothing to add.

“He has told you, O mortal, what is good.” Do justice. Love mercy. Walk humbly with God (Micah 6:8).

What does it take to be a pastor? We could speak of call, commission and cov­enant. We could speak of study and formation. But somewhere near the heart of serving God as pastor or priest — and, for that matter, as a disciple — is the prophets’ call to holiness.

Brad Roth is pastor of West Zion Mennonite Church in Mound­ridge, Kan., and author of God’s Country: Faith, Hope and the ­Future of the Rural Church ­(Herald Press). He blogs at ­DoxologyProject.com.