Remember that pride is the worst viper that is in the heart, the greatest disturber of the soul's peace and sweet communion with Christ; it was the first sin that ever was, and lies lowest in the foundation of Satan's whole building, and is the most difficultly rooted out, and is the most hidden, secret and deceitful of all lusts, and often creeps in, insensibly, into the midst of religion and sometimes under the disguise of humility.

Letter to Deborah Hatheway (1741), in Letters and Personal Writings (1998), edited by George S. Claghorn, Vol. 16.