One of the reasons Donald Trump’s speech at Liberty University electrified evangelical voters is, I suspect, that we haven’t heard on the campaign trail a great deal about religious freedom. This despite the centrality of faith in conflicts abroad and controversies at home.

Mr. Trump vowed to protect Christians being targeted by the Islamist Jihad overseas. He spoke of his own religious faith. But our country is hurtling toward a constitutional showdown over religious liberty right here in America.

That’ll come in the next month or so, when the Catholic charity known as Little Sisters of the Poor makes at the Supreme Court a gutsy gamble for protection from the birth-control mandate the Obama administration has promulgated under ObamaCare.

Guess who filed the first friend-of-the-court brief on their side.

Yes, it was Orthodox Jewish rabbis.

They know that this case isn’t about simply whether a group of nuns has to fill out paperwork to avoid being forced to pay for birthcontrol for their employees. You can bet the Ten Commandments on it.

This is about whether our increasingly socialistic system is going to stop where the First Amendment says it’s supposed to stop. It’s about the right of religious Americans to stand apart.

And it’s about George Washington’s promise to the Jews.

Washington made that promise in a famous letter to the Touro Synagogue in Rhode Island. One of the reasons it’s so important is that he wrote it in 1790, more than a year before the First Amendment was ratified.

Our first president was replying to a welcome sent to him by local Jews when he visited the Ocean State. Echoing Micah 4:4 in the Hebrew Bible, Washington prayed that “every one shall sit in safety under his own vine and fig tree and there shall be none to make him afraid.”

One way I like to put Washington’s promise is this: In America, the fact that you fear God shall be no cause to fear your government. Yet today, millions of Americans who do fear God are starting to fear their government.

Some are worried that the government will try to regulate — or even ban — circumcision. Some are wondering whether they have to host same-sex marriages if they rent out their home for traditional marriages.

Others fear they’ll be maneuvered into paying for abortions. Or that possessing eagle feathers, sacred to Apaches, will expose them to charges under laws designed to protect endangered species. (That’s an actual case.)

Like the Little Sisters, the rabbis aren’t looking out for only themselves. They argue that the Religious Freedom Restoration Act, under which the Little Sisters seek shelter, “protects all religious exercise, no matter how obscure.”

The rabbis are warning that the lower court “refused to protect the Little Sisters’ religious liberty” because the judges “found their explanations regarding the nature and significance of their religious beliefs ‘unconvincing.’”

Since when do any of us have to convince a judge of our religious beliefs?

Nor are the rabbis alone. One brief siding with the Sisters is on behalf of the Church of the Lukumi Babalu, the Society for Krishna Consciousness, the Islamic Center in Murfreesboro and a pastor and other members of the Lipan Apache Tribe.

They all sense that our country is hurtling toward a moment of truth over how seriously it takes the whole idea of religious freedom. They fear we could come unmoored from the founding promises. I keep coming back to Washington.

In addition to Rhode Island, he wrote a separate letter to Jewish communities in Philadelphia, Charleston, Richmond, and New York. He boasted of the “liberality of sentiment towards each other” held by “every political and religious denomination of men in this country.”

The foremost Founder called such sentiments a “treasure beyond the reach of calculation.” He remarked that the “power and goodness of the Almighty were strongly manifested” in America’s “glorious revolution.”

“In war he directed the sword,” Washington wrote, “and in peace he has ruled in our councils.”

That’s into what Trump tapped. The other GOP candidates get it, too. Let us trust that the Almighty has His eye on our own Supreme Court.

This column first appeared in the New York Post.