'Ali R.A said;

"The one who shows off has three charactersistics: he is lazy when by himself, he is lively and energetic when with others and he increases in his actions when he is praised and decreases in them when he is criticised."

Part of a list of sayings taken from Ihyaa Uloom id-Deen of al-Ghazaalee, Mukhtasir Minhaaj il-Qaasideen of Ibn Qudaamah and Kitaab uz-Zuhd of Ibn al-Mubaarak