In the last 5 verses of Genesis, Joseph's 110 years is written twice. The first shows 110 years of life, while the latter shows 110 years in age. Is that just repeated for no particular reason, or are life and age two different things?
The two are sometimes considered to differ by about 9 months, with life beginning at conception and age beginning at birth.
A chaism is a structure common in the Old Testament (but also found in the New Testament). It is basically text constructed in an ABCBA or ABCDCBA (or etc.) pattern. For instance, consider Luke 4
A v1-4: Jesus tempted to exercise his power over the physical world to be fed
-B v5-8: Jesus tempted to usurp authority over the world
--C v9-13: Jesus tempted to jump off a cliff to prove that God will protect him
---D v14-15: Jesus preaches the word
--C v16-30: God protects Jesus from being thrown off a cliff
-B v31-37: Jesus proves his authority, even over demons, Satan's minions
A v38-41: Jesus exercises his power over the physical world, and is fed by woman he heals
The main point that the author is trying to emphasize is generally found in the juicy center of the chiasm: in this case the emphasis is in Jesus' ministry.
It should come as no surprise at this point that I believe Gen 50:22-26 is a chiasm:
A 22 Joseph lives 110 years
-B 23 Joseph's children and their link to their ancestor Jacob
--C 24 The promise to Abraham reiterated
-B 25 Jacob's children - a look forward
A 26 Joseph dies after 110 years
The main point, then, is Joseph's reiteration of the promise to Abraham, Isaac, and Jacob. The 110 years are repeated in order to make the chiasm more obvious.
Compare the chiasm with the text itself:
22 So Joseph dwelt in Egypt, he and his father’s household. And Joseph lived one hundred and ten years.
--23 Joseph saw Ephraim’s children to the third generation. The children of Machir, the son of Manasseh, were also brought up on Joseph’s knees.
----24 And Joseph said to his brethren, “I am dying; but God will surely visit you, and bring you out of this land to the land of which He swore to Abraham, to Isaac, and to Jacob.”
--25 Then Joseph took an oath from the children of Israel, saying, “God will surely visit you, and you shall carry up my bones from here.”
26 So Joseph died, being one hundred and ten years old; and they embalmed him, and he was put in a coffin in Egypt.
There is no reason to assume that the 9 month pregnancy period should impact the ages - either they are from conception, or they are from birth - there would be no reason to oscillate between the two.
In Genesis 50:22 the text literally says:
וַיְחִ֣י יוֹסֵ֔ף מֵאָ֥ה וָעֶ֖שֶׂר שָׁנִֽים1
"Joseph lived a hundred and ten years"
In v. 26, an idiomatic expression is used to say the same thing. The text of Genesis 50:26 literally says:
בֶּן־מֵאָ֥ה וָעֶ֖שֶׂר שָׁנִ֑ים2
"son of a hundred and ten years"
This is a common idiom used for expressing age in Biblical Hebrew.3 Neither expression indicates a difference in how the age should be calculated (and I cannot find any support for different calculations in scholarly literature).
The IVP Commentary offers the following information:
Joseph dies at the age of 110, considered the ideal age for an Egyptian. Examination of mummies has demonstrated that the average life expectancy in Egypt was between forty and fifty years. The use of the coffin or sarcophagus in mummification was an Egyptian, not an Israelite, practice.4
Several sources corroborate that 110 years of age was an ideal age of death for Egyptians.5 Overall, this information is likely repeated because it demonstrates that Joseph was a successful Egyptian official, and his age of death was a cultural confirmation of this that would have been understood by the original readers.
The context of this passage affirms that Joseph was a Hebrew, not an Egyptian, and yet emphasizes his success in both cultures. His burial was finally with the Hebrews and according to Hebrew customs rather than Egyptian practices (embalming and burial vs. mummifying).6
1 Biblia Hebraica Stuttgartensia: SESB Version., electronic ed. (Stuttgart: German Bible Society, 2003), Ge 50:22.
2 Ibid., Ge 50:26.
3 Lexical entry for בֵּן: "in expressions specifying age (→ בַּת 4): aged (so much) (MHb. JArm. Palm. Syr. Arb. Soq.): בֶּן־שְׁמֹנַת יָמִים eight days old Gn 1712, בֶּן־שָׁנָה one year old Ex 125 (1S 131 the number is missing), בֶּן־שְׁנָתוֹ (“situation specification” Landsberger JNES 8:288, → יוֹם 3, חֹדֶשׁ 2, BL 5181) one year old Lv 2312 (6 ×), בֶּן־חֲמֵשׁ מֵאוֹת שָׁנָה Gn 532, בִּן־לַיְלָה one night old, meaning grown up in one night Jon 410...."
Ludwig Koehler et al., The Hebrew and Aramaic Lexicon of the Old Testament (Leiden; New York: E.J. Brill, 1999), 138.
4 Victor Harold Matthews, Mark W. Chavalas, and John H. Walton, The IVP Bible Background Commentary: Old Testament, electronic ed. (Downers Grove, IL: InterVarsity Press, 2000), Ge 50:26.
5 Marie Parsons. "Old Age in Ancient Egypt." (Tour Egypt), retrieved from the Tour Egypt website. A search for this information will reveal numerous sources showing that 110 years was an ideal age of death for Egyptians.
6 James McKeown. Genesis: Two Horizons Old Testament Commentary series. (Grand Rapids, MI: Wm. B. Eerdmans Publishing Co., 2008), 192-193.
Genesis 50:22-23 simply give the age the first time to show that he got to see his sons great-great grandchildren. Remember that Joseph was 39 Years old in the 130th Year of his father who, with the rest of his family, came down to Egypt. Joseph is 56 Years old when Jacob dies in his 147th Year: therefore Jospeh would live another 54 Years before his death. Finally vv. 24-25 are connected to the 110th Year of his life to show that he died after having lived so many years from his birth.
