On the road to Damascus — as we all remember from Bible classes — Saul of Tarsus was struck from his horse by a vision of Jesus. He immediately converted to Christianity, eventually becoming St. Paul. A familiar enough story to most of us, except that’s not what the New Testament says. No horse is ever mentioned — in all likelihood, Saul simply walked.

In an even more familiar story, the Gospel of Matthew tells of “we three kings,” the three magi coming to adore the infant Jesus. Except here, too, there’s a discrepancy: The gospel never mentions their number. It says only that wise men brought Jesus three gifts: gold, frankincense and myrrh. So where did the horse and the three kings come from?

They came from early Bible illustrations and church paintings. In other words, some of what we think we know, some of what people believe about Christianity, isn’t derived directly from the Bible; it has been filtered through centuries of artistic and scriptural interpretations. The two examples given here are small potatoes when it comes to articles of faith, of course. In fact, it’s easy to understand why the horse, for one, was added: simple visual drama (see, for instance, the famous Caravaggio,). But when one realizes that in its first four centuries, Christianity went from being an oppressed, highly inward, even secretive Jewish sect to being the most powerful, imperial church on the planet, a shareholder in the Roman Empire, then it’s plain that huge changes buffeted the religion — and its art — during its very beginnings.

This is the story told by “Picturing the Bible: The Earliest Christian Art,” the exclusive new exhibition at the Kimbell Museum through March 30, which features some 100 pieces of art, many not seen before outside of Europe. Unfortunately, much of the relevant and most impressive art from the period — paintings on catacombs, frescoes and mosaics from churches — can’t travel. Color photos must suffice, although because many on display were taken a century ago and then hand-tinted, they provide a livelier sense of the original colors than what one might see on walls in Italy, Syria or Israel today. And then, some of the photos, notably a set of carved wooden church doors from Rome, are reproduced more or less life-size. Big, in other words.

It’s also true that for reasons that are still debated, the earliest Christians didn’t seem to produce much permanent, public art (their fugitive standing inevitably contributed to this — they didn’t really have churches — but so, too, did the inward nature of the faith). Much of the art included here — sarcophagi, crucifixes, ivory figurines, bowls, reliquaries, Bibles, silverware — is actually from the the later half of the period, the third and fourth centuries. Meaning that some of these images are essentially post facto, created after a number of the epochal changes happened to the church.

Nonetheless, to take perhaps the most significant example, “Picturing the Bible” captures the fundamental shift in the image and meaning of Jesus. At first, Jesus is seen as teacher, philosopher, healer. He is depicted as little different than an ordinary man (wearing simple white garments, and sometimes even without a halo). It is his miracles, his actions and his words, that are profound. In effect, he is just a vessel for the Word of God.

But as the Roman emperor Constantine became Christian over the course of his reign — he declared religious tolerance toward the faithful with the Edict of Milan in 313 and was baptized a short while before his death in 327 — the imagery changed profoundly. Jesus becomes Jesus the Lord, Jesus the King. In the images in the exhibition, Jesus gets bigger, the halos get bigger, the raiments turn to gold and he is now often enthroned in glory, clearly holding dominion over heaven and earth.

In effect, the unassuming teacher of love wasn’t a sufficiently impressive figure to be the Power that holds the Empire together. Jesus became fused, in part, with the traditions of the divine Roman emperor.

And these weren’t just cosmetic or public-relations changes. They became enshrined in doctrine when the bishops met at the Council of Nicaea in 325 and declared that Jesus, rather than being just a wise man or a secondary spiritual figure, was equal to God the Father.

Although much of “Picturing the Bible” is small-scale and of more historical and religious import than immediate artistic appeal, curator Timothy Potts, the Kimbell director who resigned in September to take over Cambridge University’s Fitzwilliam Museum, has made sure to feature some dazzlers — including handsome silver dishes that an English farmer found while plowing in 1975 and, especially, a sixth century gold crucifix, 16 inches tall and studded with gems. It is understandably saved for last, not only because of the late date but also because few things could more stunningly illustrate the grandeur that the Church had assumed than this gift from the Byzantine emperor Justin II, which once served as a container for a piece of the True Cross.

Some works on display are also different from much church art with which we moderns are familiar. Essentially, they’re not “church” art. They’re intimate, family items for domestic use, such as a child’s sarcophagus. Or they were in catacombs, paintings that have a certain kinship with cave art. Revealingly, Jonah being swallowed by the whale was a popular story for catacomb decoration.

Such Old Testament figures as Jonah, Moses, Abraham and Isaac were favorites — partly because Christian missionaries were often preaching to Jews, partly because Christianity saw itself as fulfilling Judaic law and these figures were intended to teach converts how to read the Old Testament as prefiguring the New.

“Picturing the Bible” is not easily absorbed by the casual museum stroller looking for the high finish of Old Masters; it requires a deal of study to absorb the details. Nonetheless, it’s a remarkable undertaking for the Kimbell — deep, thoughtful, wide-ranging and in a period not normally served by museum projects of this size and caliber.

By the way, St. Paul does appear in the exhibition, although not in his conversion-on-horseback. And the magi can indeed be glimpsed on a 4th century marble sarcophagus, all three of them crowned as kings and carrying their gifts.