Salim (may Allah have mercy on him) narrates from his father that the Messenger of Allah (peace and blessings be upon him) said: "Envy is not permissible except in two cases: a man to whom Allah has given the Qur'an, and he stands with it in prayer in the hours of the night and the day; and a man to whom Allah has given wealth, and he spends it in the hours of the day and the night."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7826