"left thy first love" - Revelation 2:4
Expositor's Greek Testament, Volume V notes:

Jealous regard for moral or doctrinal purity, and unwavering loyalty in trial, so far from necessarily sustaining the spirit of charity, may exist side by side, as here, with censoriousness, suspicion, and quarrelling.

Discussion: How can we, in our attempt to remain doctrinally pure, avoid the error of Ephesus church, having "left [their] first love"?
Source: Expositor's Greek Testament, Volume V