“Whoever has the ability to speak Arabic well should not speak in a foreign tongue, for that breeds hypocrisy.”
It is also narrated with a well-known chain that reaches Abū Sahl Maḥmūd ibn ʿUmar al-ʿUkbarī: Muḥammad ibn al-Ḥasan ibn Muḥammad al-Muqriʾ told us; Aḥmad ibn al-Khalīl—while in Balkh—told us; Isḥāq ibn Ibrāhīm al-Ḥarīrī told us; ʿUmar ibn Hārūn told us, from Usāmah ibn Zayd, from Nāfiʿ, from Ibn ʿUmar, who said:
The Messenger of Allah (Allah bless him and grant him peace) said, “Whoever can speak Arabic fluently should not speak Persian, for that breeds hypocrisy.”
This statement resembles one ascribed to ʿUmar ibn al-Khaṭṭāb; as for attributing it to the Prophet, its authenticity needs clarification.
It has likewise been reported from a number of the early Muslims that they would insert an occasional non-Arabic word in their speech. Abū Khulda said, “Abū ʿĀliyah spoke to me in Persian,” and Mundhir said
(1) Al-Hakim also cites this report in al-Mustadrak, 4:87; its isnad contains Umar b. Harun, whose narrations are rejected.
(2) The printed edition reads “Abi Suhayl,” but the wording preserved in the manuscripts is sounder. See Lisan al-Mizan 6:3, no. 5.
(3) Ibn Hajar lists him in Lisan al-Mizan, 6:3, no. 5, without expressing either approval or disapproval of him.
(4) The name is probably Muhammad b. al-Hasan b. Muhammad b. Ziyad al-Mawsili, later al-Baghdadi, the celebrated Qur’an reciter and exegete nicknamed al-Naqqash; his hadiths are rejected. He was born in 266/879 and died in 351/962. See Tadhkirat al-Huffaz 2:908–9 (no. 872), part 3.
(5) Al-Hakim (al-Mustadrak 4:87) gives the name as Ahmad b. al-Layth b. al-Khalil, and I have found no biographical entry for him.
(6) All the manuscripts read “al-Hariri,” but “al-Jariri” is probably correct, as in al-Mustadrak 4:87; his biography was noted above.
(7) I have not been able to trace him.
(8) He is Khalid b. Dinar al-Tamimi al-Sa‘di, Abu Khulda, a Basran tailor; he is saduq (reliable) and belongs to the fifth generation. Al-Bukhari, al-Nasa’i, Abu Dawud and al-Tirmidhi all transmit his hadiths. See Taqrib al-Tahdhib 1:213, no. 26.
(9) Musannaf Ibn Abi Shayba 9:11, no. 6334.