What is the earliest explicit reference to the "Talmud" after it was compiled?

Question

I am thinking of perhaps the earliest direct quotation of it, or reference to it by name or at least in some manner in which it is clear that the Talmud itself is being described. Essentially, I am curious as to what the earliest evidence there is for someone having direct external knowledge of the Talmud.

Answer 1

It seems to me that you are looking for Geonic material (Saboraic writings would be interpolated into the Talmud itself). In Simhah Assaf's Tequfath ha-Geonim we-Sifrutah he writes:

In short that it is difficult to pinpoint precisely the beginning of Geonic literature, but those of the Suran Gaon, R. Sheshnah (before 689 CE) are of the earliest responsa we have. The larger more compositional type works come to us from the 8th century CE.

R. Sheshnah Gaon is seen by some as the last of the Saboraim and among others as the first of the Geonim. So he may be seen as a bridge between the periods. Among those teshubhoth of his that are extant several can be found in Sha'arei Teshubhah, Teshubhoth ha-Geonim. He explores topics such as Tefillin on 9 Abh (no. 155 and no. 266), whether the reader may say anything other than what's written while the Sefer Torah is open (no. 350), or reading any word not written therein (no. 351).

If you are interested in the topic generally, Assaf's work is excellent, as well as the more recent work by Robert Brody "The Geonim of Babylonia and the Shaping of Medieval Jewish Culture"

Answer 2

There is a work by Rav Achai Gaon called שאילתות דרב אחאי גאון, which was composed in the mid-8th century, not long after the redaction of the gemara, and it mentions the gemara many times.

It is on Sefaria here.

He is recognised as the "first Rabbinic author after the Gemara" in academic works* (which are out of date and could benefit from looking up @Deuteronomy's answer and quoted sources!), and was actually situated, along with many other early Geonim, in the same academies where the Amoraic discussions were made and noted, and finally redacted into the Talmud.

Therefore the work itself is all that is "external", external to the Talmud itself. Saying that the Gaon had "external knowledge" (OP wording) is more questionable, as that could imply someone outside the Babylonian Academies where the Talmud was born, and still sitting on the shelves :)

^{* Encyclopædia Britannica. Vol. 1 (11th ed.). Cambridge University Press. p. 429}

Answer 3

One reasonably early discussion of both the Palestinian and Babylonian Talmuds comes from the Letter of Baboi, a mid-8th century composition. Monika Amsler describes it as follows;

The traditional explanation for a considerable temporal gap between the two Talmuds is based on the “Letter of Baboi” (mid-eighth century). In this letter, Baboi claimed that the Palestinian rabbis had been forced to write down their knowledge because of the political instability of Palestine, whereas the Babylonian rabbis continued to adhere to oral transmission. In Baboi’s opinion, this rendered the Palestinian Talmud inferior to the Babylonian one. The letter is spurred by the ongoing theological discussions about the superiority of the unwritten in Baghdad at the time.77 Still, Baboi’s letter left posterity with the notion “that literary production is a rearguard action, a textual encapsulation – and in the case of the Palestinian Talmud, a hasty and haphazard one – of a once vibrant tradition put in jeopardy by outside forces or by unfulfilled messianic expectations.”78 (Amsler, The Babylonian Talmud and Late Antique Book Culture, Cambridge 2023, pg. 128)

However, there is an even earlier reference. I have come across a near-quotation of the Talmud in the Qur'an first pointed out by Abraham Geiger (1810-1874), which is widely agreed to have reached its current textual form by the end of the mid-7th century or 650 at the latest when it was canonized (Van Putten, "The Grace of God," 2019; Hythem Sidky, "On the regionality of Qurʾānic codices," 2021; Joshua Little's lecture in: https://www.youtube.com/watch?v=QN8TUNGq8zQ). Namely:

Q 5:32: Because of that We ordained for the Children of Israel: that whoever kills a person—unless it is for murder or corruption on earth—it is as if he killed the whole of mankind; and whoever saves it, it is as if he saved the whole of mankind. Our messengers came to them with clarifications, but even after that, many of them continue to commit excesses in the land.

This is how the tradition appears in the Palestinian Talmud:

PT: For this reason man was created along to teach you that whosoever destroys a single soul Scripture imputes (guilt) to him as though he had destroyed a complete world, and whosoever preserves a single soul, Scripture ascribes merit to him as though he had preserved a complete world.

The version in the Babylonian Talmud is slightly different, specifying that this only applies to a soul killed or saved in Israel. This comparison is discussed by Professor Holger Zellentin in a 2022 lecture "The Arabian Qur'an Between the Bible and Byzantium" in a symposium called Unlocking the Byzantine Quran (the name being a bit of a play on the name of a previous symposium titled Unlocking the Medinan Quran). You can find the whole thing here: https://www.youtube.com/watch?v=2f6pC7AfSOI (see 14min-20min). That this type of familiarity might have existed is no surprise, as the Qur'an itself mentions Jews, the "People of the Scripture" (or "scripture people"), the "Children of Israel", rabbis (Q 9:31), synagogues (Q 22:40), and even "scholars of the Children of Israel", that is, biblical scholars (Q 26:197). See Holger Zellentin, "banū isrāʾīl, ahl al-kitāb, al-yahūd wa-l-naṣārā: The Qur'anic Community's Encounters with Jews and Christians", Entangled Religions 2023.

The Qur'an also demonstrates other evidence of knowledge of Talmudic traditions, although none as direct as this case. A small sampling: raising a mountain above a people (Q 2:63 / b. Shabbat 88a), a divorced women must wait three months before remarrying (Q 2:228 / m. Yevamot 4:10), the requirement for a multiplicity of witnesses to make an adultery conviction (four in Q 4:15; two in Sota 2a), a command not to pray while drunk but that you may perform an ablution with ground if water is unavailable (Q 4:43; b. Berakoth 15a, 31b). References to these are in Gabriel Said Reynolds' The Quran and the Bible (Yale 2018) and Haggai Mazuz's book The Religious and Spiritual Life of the Jews of Medina (Brill 2014). Here are a few other comparisons compiled from some other academic works. The Qur'an strongly forbids associating anything with God, shirk. Angelika Neuwirth has compared this to bSuk 45b: "Whoever associates (meshattef) something else with the God of heaven, is excluded from the coming world" (Neuwirth, The Qur'an and Late Antiquity, Oxford 2019, pg. 206). Qur'anic guidelines on how a husband should deal with a wife that he suspects of infidelity in Q 4:34 are found prior in m. Sotah 1.1-4 (Saqib Hussain, "The Bitter Lot of the Rebellious Wife: Hierarchy, Obedience, and Punishment in Q. 4:34", Journal of Qur’anic Studies, 2021, esp. pp. 89-91). Finally, I note Shari Lowin's 2019 study ""The Jews Say the Hand of God is Chained": Q. 5:64 as a response to a midrash in a piyyut by R. El`azar ha-Kallir".