Probable Hadith: "Muutu qabla tamuutu" "Die before you die"
Qur'an, 2:54 (Asad): "and when Moses said unto his people: "O my people! Verily, you have sinned against yourselves by worshipping the calf; turn, then. in repentance to your Maker and mortify yourselves (faqtuluu anfusakum);  this will be the best for you in your Maker's sight". And thereupon He accepted your repentance: for, behold, He alone is the Acceptor of Repentance, the Dispenser of Grace."
Mortify yourselves, or mortify your "egos" as "anfusakum" could be "yourselves" or "your egos". I understand this "killing of the ego" to mean what Frank Parmir beautifully described below MashaAllah:
"Occasionally, some people come to 'know' that there IS One Eternal Presence apart from Whom nothing else exists. Occasionally, some people come to 'see' The One as Infinite in Goodness, Mercy, and Justice. Within the hearts of those who come to such 'gnosis,' there arises a life-long resonance of Peace and Joy that transcends every circumstance and makes of their lives an eternal paradise. What keeps the rest of us from realizing The Infinite Power and Goodness of The Real? What alternative knowing is in the rest of us that excludes us from Paradise? Is it not our belief in our own separate and permanent existence? Is it not our belief in our own wisdom, in our own power, and in our own judgment? So long as we 'know' we are separate beings, we cannot 'know' The One apart from Whom nothing else is. So long as we 'see' only our own judgment of events, we cannot see that everything within reality is an aspect of The One Creator's Goodness, Mercy, and Justice. If our belief in our own independent power and judgment is an error that separates us from Goodness, how can we come to see it so? We must look honestly and fearlessly at these 'selves' that we take to be our salvation. If we are to have good lives we must see either their undoubted power, or their pathetic poverty. If we look hard enough, the infinite richness of The Real will be found hidden behind the imagined richness of our infinitely impoverished 'selves.' "