Catena Aurea on Luke 6:1–5: Isidore of Seville

He says, On the second-first, because it was the second day of the Passover, but the first of unleavened bread. Having killed the passover, on the very next day they kept the feast of unleavened bread. And it is plain that this was so from the fact, that the Apostles plucked ears of corn and ate them, for at that time the ears are weighed down by the fruit.