Very frequently, in the New Testament, first aorist endings instead of second aorist endings are used on second aorist stems.
Examples: εἶπαν instead of εἶπον (third person plural), εἰπόν instead of εἰπέ (imperative). This usage is much more common in some parts of the aorist than in others. εἶπον in the indicative has almost exclusively first aorist forms.