It is related from Abū Hurayrah (may Allah be pleased with him) that he once said to a man whose stomach was hurting:

“Ashkam badard.”

Some narrate the report as being attributed to the Prophet, but that attribution is not sound.

As for habitually conversing in a language other than Arabic—the emblem of Islam and the language of the Qur’an—until it becomes the common practice of a town and its inhabitants, or of the people of a house, or of one man with another, or of those in the marketplace, the officials, the scribes, or the jurists, there is no doubt that this is disapproved, for it amounts to imitating the non-Arabs, and such imitation, as noted earlier, is blameworthy.

For this reason, when the early Muslims settled in Syria and Egypt, whose people originally spoke Greek, and in Iraq and Khurāsān, whose people spoke Persian, and in the Maghrib, whose people spoke Berber, they accustomed the inhabitants of those lands to Arabic until it prevailed among the populations of those cities—Muslim and unbeliever alike; such was likewise the case in ancient Khurāsān.

Later, however, they grew lax concerning the language and became accustomed to speaking Persian, until it gained the upper hand and Arabic was neglected by many of them. There is no doubt that this is reprehensible. The praiseworthy course is to make a habit of speaking Arabic so that children absorb it in the elementary schools and in the home, the emblem of Islam and its people becomes manifest, and it becomes easier for Muslims to understand the meanings of the Book, the Sunnah, and the words of the early generations. By contrast, whoever is accustomed to one language and then wishes to move to another will find the shift difficult.