A.T. Robertson Commentary 1 John 4:19

"We love, because he first loved us." — 1 John 4:19 (ASV)

He first (αυτος πρωτος). Note πρωτος (nominative), not πρωτον, as in Joh 20:4,8. God loved us

before we loved him (John 3:16). Our love is in response to his love for us. Αγαπωμεν is indicative (we love), not subjunctive (let us love) of the same form. There is no object expressed here.