John has already written about false teachers and their characteristics. Because of this, it is difficult to discern whether verse 26 concludes the previous section or introduces a new section. Perhaps John intended both. Here he discusses another characteristic of false teachers: they seek to deceive the faithful (v. 26).
Basically, John’s meaning is: because Christ’s anointing guards against spiritual deception, believers should abide in Christ to remain in truth and not be deceived.
A. Christ’s Anointing Guards You Against Spiritual Deception – (v. 26).
I. Abide in Christ to Tap Into His Truth – (v. 27).