That covetousness brings upon the soul a spiritual leprosy.
And such are seen to be lepers in spirit and heart, after the likeness of Gehazi, who, desiring the uncertain riches of this world, was covered with the taint of foul leprosy, through which he left us a clear example that every soul which is defiled with the stain of cupidity is covered with the spiritual leprosy of sin, and is counted as unclean before God with a perpetual curse.
Source: Institutes (New Advent)