Seeing that ye know these things before - Being aware of this danger, and knowing that such results may follow. People should read the Bible with the feeling that it is possible that they may fall into error, and be deceived at last. This apprehension will do much to make them diligent, and candid, and prayerful, in studying the Word of God.
With the error of the wicked - Wicked men. Such as he had referred to in 2 Peter 2, who became public teachers of religion.
Fall from your own steadfastness - Your firm adherence to the truth. The particular danger here referred to is not that of falling from grace, or from true religion, but from the firm and settled principles of religious truth into error.