And He said unto Abram: ‘Know of a surety that thy seed shall be a stranger in a land that is not theirs, and shall serve them; and they shall afflict them four hundred years; and also that nation, whom they shall serve, will I judge; and afterward shall they come out with great substance. But thou shalt go to thy fathers in peace; thou shalt be buried in a good old age. And in the fourth generation they shall come back hither; for the iniquity of the Amorite is not yet full.’ (Genesis 15:13–16)

וַיֹּאמֶר לְאַבְרָם: יָדֹעַ תֵּדַע כִּי גֵר יִהְיֶה זַרְעֲךָ בְּאֶרֶץ לֹא לָהֶם, וַעֲבָדוּם וְעִנּוּ אֹתָם אַרְבַּע מֵאוֹת שָׁנָה. וְגַם אֶת הַגּוֹי אֲשֶׁר יַעֲבֹדוּ דָּן אָנֹכִי, וְאַחֲרֵי כֵן יֵצְאוּ בִּרְכֻשׁ גָּדוֹל. וְאַתָּה תָּבוֹא אֶל אֲבֹתֶיךָ בְּשָׁלוֹם, תִּקָּבֵר בְּשֵׂיבָה טוֹבָה. וְדוֹר רְבִיעִי יָשׁוּבוּ הֵנָּה – כִּי לֹא שָׁלֵם עֲוֺן הָאֱמֹרִי עַד הֵנָּה. (בראשית ט"ו, יג-טז)

What does “the fourth generation” mean at the end of the covenant between the pieces’ prophecy?

The straightforward explanation is the fourth generation of those descending to Egypt. Four generations from the beginning of enslavement to entry into the land can be counted as follows: Kohath, Levi’s son, is the first generation of enslavement; his son Amram is the second; Amram’s son Aaron is the third; and Aaron’s son and successor Eleazar, who entered the land (Joshua 14:1), is the fourth generation returning to Canaan.

This encounters a difficulty: the prophecy speaks of four hundred years of enslavement, and such a long period usually contains far more than four generations. Moreover, the Torah explicitly gives Kohath’s and his descendants’ lifespans: Kohath lived 133 years (Exodus 6:18), Amram 137 (Exodus 6:20), and Aaron and Moses were 83 and 80 when they stood before Pharaoh on the eve of the exodus (Exodus 7:7). Even assuming Kohath was an infant on arriving in Egypt, fathered Amram in his death year, and Amram fathered Moses in his own death year, Egypt’s sojourn would total at most 350 years (133 + 137 + 80), fifty less than the covenant’s four hundred.

The common assumption is that the list provides a complete genealogy: Kohath directly Levi’s son, Amram directly Kohath’s, and so forth. An alternative explanation is that those named are only prominent figures in much longer lineages, and their relationships need not be father and son (Shadal on Exodus 6:20).

Evidence appears in Chronicles. One particularly fascinating example is Joshua son of Nun’s lineage:

And the sons of Ephraim: Shuthelah–and Bered was his son, and Tahath his son, and Eleadah his son, and Tahath his son, and Zabad his son, and Shuthelah his son–and Ezer, and Elead, whom the men of Gath that were born in the land slew, because they came down to take away their cattle. And Ephraim their father mourned many days, and his brethren came to comfort him. And he went in to his wife, and she conceived, and bore a son, and he called his name Beriah, because ait went evil with his house. And his daughter was Sheerah, who built Beth-horon the nether and the upper, and Uzzen-sheerah. And Rephah was his son, and Resheph, and Telah his son, and Tahan his son; Ladan his son, Ammihud his son, Elishama his son; Nun his son, Joshua his son. And their possessions and habitations were Beth-el and the towns thereof, and eastward Naaran, and westward Gezer, with the towns thereof; Shechem also and the towns thereof, unto Aiah and the towns thereof; (I Chronicles 7:20–28)

וּבְנֵי אֶפְרַיִם: שׁוּתָלַח וּבֶרֶד בְּנוֹ, וְתַחַת בְּנוֹ, וְאֶלְעָדָה בְנוֹ, וְתַחַת בְּנוֹ. וְזָבָד בְּנוֹ, וְשׁוּתֶלַח בְּנוֹ. וְעֵזֶר וְאֶלְעָד – וַהֲרָגוּם אַנְשֵׁי גַת הַנּוֹלָדִים בָּאָרֶץ, כִּי יָרְדו לָקַחַת אֶת מִקְנֵיהֶם. וַיִּתְאַבֵּל אֶפְרַיִם אֲבִיהֶם יָמִים רַבִּים, וַיָּבֹאוּ אֶחָיו לְנַחֲמוֹ. וַיָּבֹא אֶל אִשְׁתּוֹ וַתַּהַר וַתֵּלֶד בֵּן וַיִּקְרָא אֶת שְׁמוֹ בְּרִיעָה, כִּי בְרָעָה הָיְתָה בְּבֵיתוֹ. וּבִתּוֹ שֶׁאֱרָה – וַתִּבֶן אֶת בֵּית חוֹרוֹן הַתַּחְתּוֹן וְאֶת הָעֶלְיוֹן וְאֵת אֻזֵּן שֶׁאֱרָה. וְרֶפַח בְּנוֹ, וְרֶשֶׁף וְתֶלַח בְּנו, וְתַחַן בְּנוֹ. לַעְדָּן בְּנוֹ, עַמִּיהוּד בְּנוֹ, אֱלִישָׁמָע בְּנוֹ. נוֹן בְּנוֹ, יְהוֹשֻׁעַ בְּנוֹ. וַאֲחֻזָּתָם וּמֹשְׁבוֹתָם: בֵּית אֵל וּבְנֹתֶיהָ, וְלַמִּזְרָח – נַעֲרָן וְלַמַּעֲרָב – גֶּזֶר וּבְנֹתֶיהָ, וּשְׁכֶם וּבְנֹתֶיהָ, עַד עַיָּה וּבְנֹתֶיהָ. (דה"א ז', כ-כח)

According to Chronicles, Joseph’s son Ephraim and Ephraim’s children lived in the land of Israel and even established settlements there. This contradicts Genesis’s account that Ephraim was born to Joseph in Egypt, and the Torah’s account of Jacob’s entire family’s descent to Egypt and return only after 430 years there and forty years of wilderness wandering.

Reconciling the contradiction lies beyond this discussion. Chronicles nevertheless indicates many more generations between those listed as descending to Egypt and those returning to Israel than the Torah describes. While the Torah lists only five generations from Jacob to Aaron’s son Eleazar, Chronicles gives eleven or even twelve, strengthening the possibility that the Torah’s lists are incomplete.

At the end of Joshua’s lineage in Chronicles, we recognize Ammihud – Elishama – Nun – Joshua. Elishama son of Ammihud served as Ephraim’s prince in the second year after the exodus (Numbers 7:48), presumably one of his tribe’s elders and dignitaries. His grandson Joshua served Moses. Joshua is called “a young man” (Exodus 33:11), suggesting he was not old. He was chosen to scout the land (Numbers 13:16), a military task, so presumably was of military age, at least twenty. Assuming twenty-five years between generations, Nun would have been about forty-five, and Joshua’s grandfather Elishama about seventy.

Seventy was very old then. The Torah recounts some exceptionally long lives, but as far as we know life expectancy was much shorter, so those exceptions do not characterize the norm. We may therefore suppose that Elishama’s father Ammihud was no longer alive at the exodus.

We must also remember a crucial detail. Although Joshua brought Israel into Canaan, his generation, the wilderness generation, died there without entering the land. The generation that entered was therefore that of his children, rather than his own.

We may thus interpret “And in the fourth generation they shall come back hither” as referring to the fourth generation among Israelites leaving Egypt, who would enter the land, rather than the fourth generation of those descending to Egypt, as commonly understood.

The first exodus generation is Elishama son of Ammihud’s, representing the congregation’s elders and princes. The second is Nun’s, Joshua’s father’s; the third is Joshua’s. Following the scouts’ sin, these three generations were sentenced to die in the wilderness. Their children, the fourth generation among those leaving, entered the land; of them it says, “And in the fourth generation they shall come back hither.”