It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Have true modesty before Allah." The Companions said: O Messenger of Allah! We do have modesty, all praise is for Allah. He (peace and blessings be upon him) said: "That is not what is meant. Rather, whoever would have true modesty before Allah, let him guard the head and what it contains, and guard the stomach and what it holds, and let him remember death and decay. And whoever desires the Hereafter abandons the adornment of this world. So whoever does that has truly had modesty before Allah."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10252