Hidden within the biblical story of Abraham, there had always been a commentary on the relative status of Israelites and Arabs. The nomadic Bedouin tribes that inhabited the part of Arabia near Israel were known as Ishmaelites, because they were thought to be descendants of Ishmael. So the Bible’s depiction of Ishmael is, implicitly, a depiction of Ishmaelites, of Arabs as they were known to the ancient Israelites.

And how is Ishmael viewed through Israelite eyes? The good news for Ishmael is that he was an offspring of Abraham’s. The bad news is that he was the child of Abraham’s slave Hagar. He thus ranked below Abraham’s son Isaac, who was born of Abraham’s wife Sarah and from whom the Israelites descended.

As if this didn’t bode sufficiently ill for the social status of Arabs, consider the circumstances of Ishmael’s birth. According to Genesis, Sarah drives the pregnant Hagar into the desert to bear her child alone. And later Sarah abandons her child in the desert. An angel prophesies his fate in a way that doesn’t bespeak a favorable Israelite view of Arabs: “He will be a wild ass of a man, his fist against all, and everyone’s fist against him.”

Naturally, Muhammad was inclined to cast Ishmael, father of the Arabs, in a more flattering light. And here he didn’t have to break radically new ground. For there was a second biblical view of Ishmael, a more flattering view, subtly woven into the Hebrew Bible alongside the first one. It was put there by P—the “Priestly source,” the author (or authors) who, as we’ve seen, seems to have reflected the aims of the Persian Empire at the end of the Babylonian exile. Judging by P’s depiction of Ishmael, Cyrus the Great must have wanted his Israelite subjects to live in peace with their Arab neighbors, on terms of mutual respect. (This would make sense. His great enemy in that area was Egypt, and the last thing he needed was for the Bedouins of Arabia to ally with their Egyptian neighbors against his empire.)

The difference between the Bible’s pre-exilic view of Ishmael and its postexilic view as presented by P is so stark that the biblical narrative, read closely, borders on the incoherent. In a pre-exilic verse Sarah, unable to bear children, encourages Abraham to take the Egyptian Hagar as a convenient concubine. “Go in to my slave-girl; it may be that I shall obtain children by her.” But in the subsequent verse, written after the exile by P, Hagar is no mere concubine; she is Abraham’s “wife,” and the polygamous marriage has Sarah’s blessing. And, whereas the pre-exilic verse has Hagar giving birth alone in the desert, a Priestly verse suggests that Abraham is present, for it is Abraham who names the newborn child Ishmael.

And as for the pre-exilic angelic prophecy that Ishmael will be a “wild ass of a man”—according to the Priestly source, God himself has higher hopes. Abraham asks God to look after Ishmael and God replies: “I will bless him and make him fruitful and exceedingly numerous; he shall be the father of twelve princes, and I will make him a great nation.”

Even in the eyes of P, Arabs don’t quite rank up there with Israelites. Immediately after shedding kind words on Ishmael, God says, “But my covenant I will establish with Isaac, whom Sarah shall bear to you at this season next year.” So it is Isaac, progenitor of the Israelites, not Ishmael, father of the Arabs, who mediates the contract with God. Still, if the Arabs aren’t quite Israelites, they’re close. The one thing this covenant demands is that Abraham’s offspring—God’s people—should be circumcised if they’re males. And Ishmael, according to the Priestly source, gets circumcised—on the same day as Abraham, no less.

By depicting Ishmael as Abraham’s beloved son, P had given Muhammad a theme he could amplify. In Muhammad’s account Abraham and Ishmael somehow wind up in Mecca together, where they build and purify the Ka’ba so that the God of Abraham can be worshipped there. What’s more, this was part of a “covenant” God had made with Ishmael and Abraham.

Talk about a grand unifying narrative! By making Abraham co-builder of the Ka’ba, Muhammad had taken the most ancient sacred figure in Jewish and Christian tradition and linked him to the most sacred shrine for Arab polytheists. Just about every religious tradition represented in Muhammad’s vicinity could find a touchstone in the religion he was creating. It was an ingenious way to try to bring all the peoples in the area under a single roof.