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 be pleased with 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 be pleased with them – 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, when he was ninety years old.

“I wish I were fluent in Arabic,”

Al-Dhahabî, Siyar A’lâm Al-Nubalâ`, in his biography of ‘Attâ b. Abî Rabâh.

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.