In Bahya ben Asher's commentary to Parashat Bereshit, the following sentence occurs: The Sage said, "Know your souls and you will know your God" (De'u nafshotekhem ve-tide'u elohekhem), which might also be translated "Know yourself . . ." The source seems to be a ḥadith quoted often by the Sufis, in which Muhammad says, "He who knows himself knows his Lord." Is it possible that Bahya would quote a ḥadith? He did live in Muslim Spain, but would he be likely to quote the words of Muhammad in a Torah commentary?
University of Arkansas
C. D. Chavel, the editor of the Mossad haRav Kook edition of the commentary, is uncertain about the source and refers to Davidson "Otzar HaMeshalim v'ha-Pitgamim", p. 85 #1330. There are several similar sources listed there, including the very one from Rabbenu Bahya. The first source listed is from Musarei haPhilosofim by Hanin ibn As-haq (Iraq, 808-873 or 877 CE), translated to Hebrew by Yehuda Alharizi (12th-13th cent). In the first "Gate", Chapter 13, seven Greek sages offer pithy sayings, with the third hakham saying that we should strive to know ourselves before undertaking knowledge of our Lord. It could be that the Sufi hadith you suggest and Musarei haPhilosofim are related somehow.
In Iggeret HaVikuah, p. 13, Shem-Tov ibn Falaquera also cites a "hakham". The saying is virtually identical to R. Bahya's citation. This seems to me like his most likely source (however, Chavel, aware of these sources, left the matter open).
Leor Jacobi, Bar-Ilan University
Bahya Ben Asher “Know your soul and you will know your God":
For this hadith and its influence in Jewish and Islamic circles see the magisterial study by Alexander Altmann, The Delphic Maxim in Medieval Islam and Judaism, in: Biblical and Other Studies, ed. by A. Altmann (Cambridge., Mass. 1963): 196-232.
This is a very typical "Sufi hadith" (i.e., put in the mouth of the Prophet or perhaps other prominent individuals, but not reported or not considered authentic by the standard collections of sound or good hadiths). I quickly found references to it in many places; most of the Islamic websites quote authorities denying that it is an authentic hadith, although Bahya would presumably have known about it from Sufi sources, not from Bukhari or Muslim ibn al-Hajjaj. And many Muslims argue that the meaning is consistent with Scripture (i.e. Quran) even if the ascription to Muhammad is unfounded.
Bahya would not have been alone among Jewish authors in reading Sufi or Philosophical works in Arabic, or using sources that did.
Among the interesting references I quickly found is one reporting it as part of the "Israiliyyat" - i.e., knowledge gained from Jewish sources. http://www.livingislam.org/k/khkr_e.html - quoting al-Fayruzabadi (15th century), Sifr al-Sa'ada--it's not clear to me that Fayruzabadi would have specifically had Bahya in front of him either.
Univ. of Wyoming
Thanks for a fascinating question! Here are my findings and comments on your query.
1. "Know Yourself and You will Know Your God" is an extended version of the Delphic maxim, "Know Yourself" (gnothi seauton). It was cited by the Ikhwan al-safa' (Brethren of Purity), Ibn Sina, al-Ghazali, Ibn Rushd, and Ibn 'Arabi, among others, and in different variants. On the usage of this dictum by Muslims and Jews, see Alexander Altman, “The Delphic Maxim in Medieval Islam and Judaism," in idem, Studies in Religious Philosophy and Mysticism (Ithaca, 1969), pp. 1-40; Adena Tanenbaum, "The Motif of Self-Knowledge: 'From My Flesh I Behold God,'" in idem, The Contemplative Soul: Hebrew Poetry and Philosophical Theory in Medieval Spain (Leiden, 2002), pp. 160-173; Diana Lobel, A Sufi-Jewish Dialogue: Philosophy and Mysticism in Baḥya Ibn Paqūda's Duties of the Heart (Philadelphia, 2007), pp. 128-129; Gyongyi Hegedus, Saadya Gaon: The Double Path of the Mystic and the Rationalist (Leiden, 2013), pp. 195-197; Joseph Yahalom, "Sa'id ben Babshad and the Early Contacts with Arabic Literature" [Hebrew], Tarbiz, 74 (2005): 371-388, at 372-373; Michael A. Sells, Mystical Languages of Unsaying (Chicago, 1994), p. 257 n. 22; Dom Sylvester Houédard, "Notes on the More than Human Saying: 'Unless You Know Yourself You Cannot Know God,'" http://www.ibnarabisociety.org/articles/notesonsaying.html.
2. Jewish citation of a Hadith (while omitting its attribution to the Prophet of Islam) might not be that unusual if one considers it to be of some "ancient" source, and not necessarily of Islamic character, as in the case of the Greek maxim. Moreover, it is not necessary that citations or phrases that were indeed borrowed from Islamic literature, such as the Qur'an, Hadith compilations, poetry, and Sufi writings, and were used in everyday Arabic among Muslims and non-Muslims alike, were considered to be problematic for Jews to be used in their literature.
3. Another approach, a more apologetic one, would be justifying the usage of Muslim religious literature for the sake of biblical commentary. This was the approach, for example, of Joseph ibn 'Aqnin (d. c. 1220) in his commentary on the Song of Songs. In the epilogue of his work, Ibn 'Aqnin praises Hai Gaon for his knowledge of the Qur'an (!) and the Hadith, and reports that Hai was once ready to consult the Christian Patriarch in order to understand the meaning of Ps. 151:5. He argues, citing BT Megillah 16a: Kol ha-omer devar hokhmah afilu be-ummot ha-'olam nikra hakham (Anyone who speaks wisdom — even if he is from among the nations of the world — is called a wise man). Ibn 'Aqnin also commands Saadia Gaon's knowledge of the Arabic (i.e. Muslim) sources.
On the rendering of Muslim sources by Jewish writers, see my Ph.D. dissertation, "'All the Kings of Arabia are Seeking Your Counsel and Advice': Intellectual and Cultural Exchange between Jews and Muslims in the Later Middle Islamic Period" (University of Chicago, 2016), chapters 1 and 2, and esp. pp. 42-44; Ibn 'Aqnin, Hitgalut ha-sodot ve-hofaʻat ha-me'orot [Inkishaf al-asrar wa-zuhur al-anwar], ed. A.S. Halkin, Jerusalem, 1964, ff. 127a-127b (in Judeo-Arabic and Hebrew translation) (notice also Halkin's citation of a Hadith with a similar message to Megillah 16a: "Take wisdom even if it is according to the sayings of the unbelievers [min al-sunna al-mushrikin]"); Eliezer Scholssberg, "Islamic Influences in Medieval Commentaries on the Bible" [Hebrew], Mahanayim, 1 (1991): 92-105 (see esp. the citations from Ibn 'Aqnin and Moshe ibn Ezra on p. 100); Hava Lazarus-Yafeh, "Jewish Knowledge of, and Attitudes towards, the Qur'an," in idem, Intertwined Worlds: Medieval Islam and Bible Criticism (Princeton, 1992), pp. 143-160; Joshua Blau, “Between Judeo-Arabic and the Qur’an” [Hebrew], Tarbiz, 40 (1971): 512-514; Moshe Gottstein, “Translations and Translators in the Middle Ages: I. Biblical Verses and Sayings of the Sages of Blessed Memory in the Translation of al-Ghazālī’s Mizān al-‘amal” [Hebrew], Tarbiz, 23 (1952): 210-216; Jonathan Kearney, “The Torah of Israel in the Tongue of Ishmael: Saadia Gaon and His Arabic Translation of the Pentateuch”, Proceedings of the Irish Biblical Association, 33-34 (2010-11): 55-75; David M. Freidenreich, "The Use of Islamic Sources in Saadiah Gaon's Tafsīr of the Torah," Jewish Quarterly Review, 93 (2003): 353-395; Jonathan P. Decter, "The Rendering of Qur'anic Quotations in Hebrew Translations of Islamic Texts," Jewish Quarterly Review, 96 (2006): 336-358; Nathan Hofer, “Scriptural Substitutions and Anonymous Citations: Judaization as Rhetorical Strategy in a Jewish Sufi Text,” Numen, 61 (2014): 364-395; Joseph Dana, "Bible and Qur’ān in the Poetics of Moses Ibn Ezra” [Hebrew], Beit Mikra, 76 (1978): 89-93; idem, "The Influence of Arabic Literary Culture on the Judeo-Arabic Literature of the Middle Ages as Reflected in Moses Ibn Ezra’a Kitāb al-Muḥāḍara wal-mudhākara [Book of Conversations and Discussions]” [Hebrew], Sefunot, 5 (20) (1991): 21-35 (pp. 28-31 on Qur'anic citations; p. 31 on citations from the Hadith); idem, "Aphorisms as an Integral Part of Judaeo-Arabic Culture (Examples from Rabbi Moshe ibn Ezra)," in Judaeo-Arabic Culture in al-Andalus, ed. Amir Ashur (Córdoba, 2013), pp. 31-50; S.J. Pearce, "'The Types of Wisdom are Two in Number': Judah ibn Tibbon’s Quotation from the Iḥyā’ ’ulūm al-Dīn," Medieval Encounters, 19 (2013): 137-166; idem, The Andalusi Literary and Intellectual Tradition: The Role of Arabic in Judah ibn Tibbon's Ethical Will (Bloomington; Indianapolis, 2016).
Judaic Studies, Yale University