Hadith 17:978
Waki’ narrated to us, from Abu Hilal, from Ibn Buraydah, who said: Umar said: "A man does not learn Persian except that he becomes deceitful, and he does not become deceitful except that his chivalry (muru'ah) diminishes."
حدثنا وكيع عن أبي هلال عن بن بريدة قال قال عمر ما تعلم الرجل الفارسية إلا خبث ولا خبث إلا نقصت مروءته