Jesus’ language is that of a jilted lover; he later identifies himself as the Bridegroom (Revelation 19:7; Revelation 21:2, Revelation 21:9). He had done so much for his bride (see Ephesians 5:25–27; Ezekiel 16:8–14), and his bride initially showed deep appreciation for his sacrifice (see Jeremiah 2:2). But that love has cooled; she abandoned that initial love. The love that’s meant here is their love for God and so for Christ, and such love exhibits itself in love for the brethren. Acts 2:41–47 gives an illustration of what that love looks like (see 1 John 3:16).
4 But I have this against you, that you have abandoned the love you had at first.