One of the reported instructions 'Umar wrote to Abû Mûsâ Al-Ash'arî and those under his governance during the former's Caliphate was, "Seek knowledge and understanding of (fiqh) the Sunnah and seek knowledge and understanding of Arabic." Ibn Abî Shaybah, *Al-Musannaf* Vol.6 p126.
It is reported that he said, "Learn Arabic, for it strengthens the intelligence and increases one's noble conduct (al-murû`ah)." Al-Bayhaqî, *Shu'ab Al-Îmân* Vol.4 p187. It is also reported that he said, "Do not learn the language of the non-Arabs, and do not enter upon them in their churches on their festivals, for indeed wrath descends upon them." 'Abd Al-Razzâq Al-San'ânî, *Al-Musannaf* Vol.1 p411. It is also reported that he was once circumambulating the Ka'bah when he heard two men speaking in a language other than Arabic behind him. He turned to them and said, "Find some way to learn Arabic." 'Abd Al-Razzâq Al-San'ânî, *Al-Musannaf* Vol.5 p496. It is reported that Ubay b. Ka'b - Allâh have mercy on him- said, "Learn Arabic just as you learn to memorize the Qurân." Ibn Abî Shaybah, *Al-Musannaf* Vol.7 p150. It is reported that Ibn 'Umar - Allâh have mercy on him - used to hit his children for making language errors. *Tahdhîb Al-Tahdhîb* Vol.9 p292. It is reported that Shu'bah - Allâh have mercy on him - said, "Learn Arabic, for it increases the intelligence." *Tahdhîb Al-Tahdhîb* Vol.4 p303. It is reported that 'Attâ b. Abî Rabâh - Allâh have mercy on him - said, "I wish I were fluent in Arabic," when he was ninety years old. Al-Dhahabî, *Siyar A'lâm Al-Nubalâ`,* in his biography of 'Attâ b. Abî Rabâ h. It is reported that Ibn Shubrumah - Allâh have mercy on him - said, "Men have never worn a garment more beautiful than Arabic." Al-Bayhaqî, *Shu'ab Al-Îmân* Vol.4 p197. *Source:* Sayings of the Salaf Blogspot