One of the reported instructions ʿUmar wrote to Abū Mūsā Al-Ash’arī 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 Abī Shaybah, Al-Muṣannaf Vol.6 p126.

It is reported that he said, “Learn Arabic, for it strengthens the intelligence and increases one’s noble conduct (al-murū`ah).”

Al-Bayhaqī, Shu’ab Al-Īmān 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.”

ʿAbd Al-Razzāq Al-Ṣan’ānī, Al-Muṣannaf 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.”

ʿAbd Al-Razzāq Al-Ṣan’ānī, Al-Muṣannaf Vol.5 p496.

It is reported that Ubay b. Ka’b – Allāh be pleased with him – said, “Learn Arabic just as you learn to memorize the Qurān.”

Ibn Abī Shaybah, Al-Muṣannaf Vol.7 p150.

It is reported that Ibn ʿUmar – Allāh be pleased with them – used to hit his children for making language errors.

Tahdhīb Al-Tahdhīb Vol.9 p292.

It is reported that Shu’bah – Allāh have mercy on him – said, “Learn Arabic, for it increases the intelligence.”

Tahdhīb Al-Tahdhīb Vol.4 p303.

It is reported that ‘Attā b. Abī Rabāḥ – Allāh have mercy on him – said, “I wish I were fluent in Arabic,” when he was ninety years old.

Al-Dhahabī, Siyar A’lām Al-Nubalā`, in his biography of ‘Attā b. Abī Rabāh.

It is reported that Ibn Shubrumah – Allāh have mercy on him – said, “Men have never worn a garment more beautiful than Arabic.”

Al-Bayhaqī, Shu’ab Al-Īmān Vol.4 p197.