I came across this in a book called Letters along the way by Don Carson and John Woodbridge (it, incidentally, is well worth a read for its inspiring portrayal of a long-distance but authentic discipleship relationship, not to mention the wise content of the letters themselves).
Jonathan Edwards on spiritual pride:
It is “the main door by which the devil comes into the hearts of those that are zealous for the advancement of religion… Spiritual pride disposes us to speak of other persons’ sins, their enmity against God and His people, the miserable delusion of hypocrites and their enmity against vital piety, and the deadness of some saints, with bitterness, or with laughter and levity, and an air of contempt; whereas pure Christian humility rather disposes, either to be silent about them, or to speak of them with grief and pity.
Spiritual pride is very apt to suspect others; whereas a humble saint is most jealous of himself; he is so suspicious of nothing in the world as he is of his own heart. The spiritually proud person is apt to find fault with other saints, that they are low in grace, and to be much in observing how cold and dead they be, and crying out of them for it; and to be quick to discern and take notice of their deficiencies: but the eminently humble Christian has so much to do at home, and sees so much evil in his own heart, and is so concerned about it, that his is not apt to be very busy with others’ hearts; he complains most of himself, and cries out of his own coldness and lowness in grace, and is apt to esteem others better than himself.”
Praise God for honest mirrors for our often self-deceiving hearts.