All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
Al-Bayhaqi in Shu’ab Al-Eemaan, and Al-Khateeb in Al-Jaami’, reported from ‘Abdul Waarith ibn Sa’eed Al-Anbari, who said, “Abu Muslim reported to me fifty years ago that ‘Umar Ibn al-Khattaab said, 'Learn Arabic as it increases Muroo'ah (noble conduct).'”
Abu Muslim is unknown. Ibn Muflih said in Al-Aadaab Ash-Shar’iyyah, “Ibn Abu Shaybah reported from ‘Umar, who said, 'Learn Arabic, for it strengthens the intelligence and increases noble conduct.' However, its chain of narrators is weak.”
Nonetheless, Ibn Al-Ja'd and Abu ‘Awaanah reported in Al-Mustakhraj from Abu ‘Uthmaan An-Nahdi, who said, “We received the letter of ‘Umar ibn Al-Khattaab while we were in Azerbaijan, and it included, 'Learn Arabic,' without the phrase, 'as it increases noble conduct.' The report is found in Saheeh Al-Bukhari and Saheeh Muslim without the mention of learning Arabic.”
For more benefit, please refer to fatwa 86262.
Allaah knows best.