Jamieson, Fausset and Brown on Revelation 2:4

4. somewhat ... because--Translate, "I have against thee (this) that," &c. It is not a mere somewhat"; it is everything. How characteristic of our gracious Lord, that He puts foremost all He can find to approve, and only after this notes the shortcomings!

left thy first love--to Christ. Compare 1Ti 5:12, "cast off their first faith." See the Ephesians' first love, Ep 1:15. This epistle was written under Domitian, when thirty years had elapsed since Paul had written his Epistle to them. Their warmth of love had given place to a lifeless orthodoxy. Compare Paul's view of faith so called without love, 1Co 13:2.