Gregory the Great — as excerpted in the Catena Aurea on Matthew 20:1-16

“(ubi sup.) The eleventh hour is that from the coming of the Lord to the end of the world. The labourer in the morning, at the third, sixth, and ninth hours, denotes the ancient Hebrew people, which in its elect from the very beginning of the world, while it zealously and with right faith served the Lord, ceased not to labour in the husbandry of the vineyard. But at the eleventh the Gentiles are called. For they who through so many ages of the world had neglected to labour for their living, were they who had stood the whole day idle. But consider their answer; They say unto him, Because no man hath hired us; for neither Patriarch nor Prophet had come to them. And what is it to say, No man hath hired us, but to say, None has preached to us the way of life,”