In Sanhedrin 69b, the gemara cites a verse to try to show that, in earlier times, men fathered children at earlier ages, even at the age of eight.
וְדוֹרוֹת הָרִאשׁוֹנִים מְנָלַן דְּאוֹלִיד? אִילֵּימָא מִדִּכְתִיב: ״הֲלוֹא זֹאת בַּת שֶׁבַע בַּת אֱלִיעָם אֵשֶׁת אוּרִיָּה הַחִתִּי״, וּכְתִיב: ״אֱלִיעָם בֶּן אֲחִיתֹפֶל הַגִּלֹנִי״, וּכְתִיב: ״וַיִּשְׁלַח בְּיַד נָתָן הַנָּבִיא וַיִּקְרָא אֶת שְׁמוֹ יְדִידְיָהּ בַּעֲבוּר (כִּי) ה׳ (אֲהֵבוֹ)״.
The Gemara asks: And from where do we derive that in earlier generations men fathered children at this age? If we say that we know this from the following calculation: It is written: “Is this not Bathsheba, daughter of Eliam, wife of Uriah the Hittite?” (II Samuel 11:3). And it is also written: “And Eliam, son of Ahithophel the Gilonite” (II Samuel 23:34), which teaches that Bathsheba was the granddaughter of Ahithophel. And it is written with reference to the birth of Solomon: “And he sent by the hand of Nathan the prophet, and he called his name Jedidiah, for the Lord’s sake” (II Samuel 12:25).
The thing is, this Sefaria text is correct. And it matches what we see in all the manuscripts, and at least one printing (Barco).
It diverged in Venice, where the verse instead purportedly ends ba’avur ki Hashem aheivo. Vilna copies this erroneous text but immediately corrects it, by parenthesizing the two spurious words, ki and aheivo.
Where did they come from? Well, firstly the verse as written is quite awkward. Because of Hashem? Because of Hashem what? The Koren English translation in Sefaria makes it for the Lord’s sake. But some commentators understand that it was because of Hashem’s love. After all:
The very name is Yedidyah, thus someone that Hashem holds dear.
The immediately preceding verse says that Hashem loved him.
Thus, II Samuel 12:24 reads:
וַיְנַחֵ֣ם דָּוִ֗ד אֵ֚ת בַּת־שֶׁ֣בַע אִשְׁתּ֔וֹ וַיָּבֹ֥א אֵלֶ֖יהָ וַיִּשְׁכַּ֣ב עִמָּ֑הּ וַתֵּ֣לֶד בֵּ֗ן (ויקרא) [וַתִּקְרָ֤א] אֶת־שְׁמוֹ֙ שְׁלֹמֹ֔ה וַיהֹוָ֖ה אֲהֵבֽוֹ׃
David consoled his wife Bathsheba; he went to her and lay with her. She bore a son and she named him Solomon. The LORD favored him,
The printer, or the scribe the printer copied from, mentally transferred the end of the preceding verse onto this one. I don’t think that it is any evidence of a variant in the Biblical verse itself. Biblical verses can sometimes be awkward.
There are some interesting variants in the initial quote about the nature of the basic dispute between Bet Shammai and Bet Hillel.
אָמַר רַבִּי חִיָּיא בְּרֵיהּ דְּרַבָּה בַּר נַחְמָנִי: אָמַר רַב חִסְדָּא, וְאָמְרִי לַהּ אָמַר רַב חִסְדָּא אָמַר זְעֵירִי: הַכֹּל מוֹדִים בְּבֶן תֵּשַׁע שָׁנִים וְיוֹם אֶחָד שֶׁבִּיאָתוֹ בִּיאָה, פָּחוֹת מִבֶּן שְׁמֹנֶה שֶׁאֵין בִּיאָתוֹ בִּיאָה. לֹא נֶחְלְקוּ אֶלָּא בְּבֶן שְׁמֹנֶה, דְּבֵית שַׁמַּאי סָבְרִי: גָּמְרִינַן מִדּוֹרוֹת הָרִאשׁוֹנִים, וּבֵית הִלֵּל סָבְרִי: לָא גָּמְרִינַן מִדּוֹרוֹת הָרִאשׁוֹנִים.
Rabbi Ḥiyya, son of Rabba bar Naḥmani, says that Rav Ḥisda says, and some say that Rav Ḥisda says that Ze’eiri says: All, i.e., both Beit Shammai and Beit Hillel, concede with regard to a boy nine years and one day old that his intercourse is regarded as intercourse and disqualifies a woman from marrying into the priesthood as well as results in her liability to receive the death penalty, even though he himself is not liable to receive it. And they also all concede concerning a boy less than eight years old that his intercourse is not regarded as intercourse vis-à-vis these halakhot. They disagree only about a boy who is eight years old, as Beit Shammai maintain that we learn from earlier generations, when people were able to father children at that age, and we apply that reality to the present; and Beit Hillel maintain that we do not learn from earlier generations.
I think that this chain, as reported, is likely wrong. And that the two variants is either a long chain starting at Rabbi Chiyya bar Rabba bar Nachmani → Rav Chisda → Rav, or that the last link in the chain is Zeiri, such that it is Rabbi Chiyya bar Rabba bar Nachmani → Rav Chisda → Zeiri. Look at the manuscripts to see what I mean.
Thus, some will express it with just Zeiri as the alternative.
And the chain does not typically end at Rav Chisda in the first place, as in Munich:
Reuchlin 2 has just a single version of the quote, which is something I like to see — the idea that these were side by side manuscripts with variants, and a scribe copied them and incorporated them together with a ve’amri lah.
By the way, I find it interesting that these Amoraim frame the dispute between Beit Shammai and Beit Hillel as whether an old scientific reality still has halachic validity.
That is, as I understand it, both Bet Shammai and Bet Hillel agree that reality changed, and ever eight years old were able to father children, something no longer true even in Mishnaic times. However, does a change in scientific reality spark a change in halachic application? And, Beit Hillel say that indeed, scientific changes to reality should lead to a different application.