6 Let none then, brethren, say, I am not of this world. Whoever you are as a man, you are of this world; but He who made the world came to you, and delivered you from this world. If the world delights you, you wish always to be unclean (immundus); but if this world no longer delight you, you are already clean (mundus). And yet, if through some infirmity the world still delight you, let Him who cleanses (mundat) dwell in you, and thou too shall be clean. But if you are once clean, you will not continue in the world; neither will you hear what was heard by the Jews, “You shall die in your sins.”
For we are all born with sin; we have all in living added to that wherein we were born, and have since become more of the world than when we were born of our parents. And where should we be, had He not come, who was wholly free from sin, to expiate all sin? And so, because in Him the Jews believed not, they deservedly heard [the sentence], “You shall die in your sins;” for in no way could ye, who were born with sin, be without sin; and yet, said He, if you believe in me, although it is still true that you were born with sin, yet in your sin you shall not die.
The whole misery, then, of the Jews was just this, not to have sin, but to die in their sins. From this it is that every Christian ought to seek to escape; because of this we have recourse to baptism; on this account do those whose lives are in danger from sickness or any other cause become anxious for help; for this also is the sucking child carried by his mother with pious hands to the church, that he may not go out into the world without baptism, and die in the sin wherein he was born. Most wretched surely the condition and miserable the lot of these men, who heard from those truth-speaking lips, “You shall die in your sins!”
Source: Tractates on the Gospel of John (New Advent)