Matthew 20:6

But this, Why stand ye here all the day idle? is not said to such as having begun in the spirit (Gal. 3:3) have been made perfect by the flesh, as inviting them to return again, and to live in the Spirit. This we speak not to dissuade prodigal sons, who have consumed their substance of evangelic doctrine in riotous living, from returning to their father's house; but because they are not like those who sinned in their youth, before they had learnt the things of the faith.

(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, Or otherwise. The morning is our childhood; the third hour may be understood as our youth, the sun as it were mounting to his height is the advance of the heat of age; the sixth hour is manhood, when the sun is steady in his meridian height, representing as it were the maturity of strength; by the ninth is understood old age, in which the sun descends from his vertical height, as our age falls away from the fervour of youth; the eleventh hour is that age which is called decrepit, and doting. They then who have neglected till extreme old age to live unto God, have stood idle to the eleventh hour, yet even these the master of the household calls, and oftentimes gives them their reward before other, inasmuch as they depart out of the body into the kingdom before those that seemed to be called in their childhood.

But at the eleventh hour the Gentiles are called, to whom it is also said: Why do you stand here idle all day? For those who, after so long a time of the world had passed, had neglected to labor for their life, stood idle, as it were, all day. But consider, brothers, what they answer when questioned: For they say: Because no one has hired us. Indeed, no patriarch, no prophet had come to them. And what does it mean to say: No one has hired us for labor, except: No one has preached to us the ways of life? What then shall we, who cease from good work, say in our excuse, we who came to the faith almost from our mother's womb, who heard the words of life from the very cradle, who from the breasts of holy Church have drunk the draught of heavenly preaching along with the milk of the flesh? We can indeed also distinguish these same diversities of hours according to the stages of ages for each individual person. For the morning of our understanding is childhood. The third hour can be understood as adolescence, because the sun, as it were, advances higher as the heat of age increases. The sixth hour is youth, because the sun is fixed as if at its center, while in that age the fullness of strength is established. The ninth hour is understood as old age, in which the sun descends as if from its high axis, because that age declines from the heat of youth. The eleventh hour is that age which is called decrepit or advanced. Hence the Greeks call the very elderly not γέροντας but πρεσβυτέρους, to indicate that those whom they call more advanced are more than old. Therefore, since one person is led to a good life in childhood, another in adolescence, another in youth, another in old age, another in decrepit age, workers are called to the vineyard at different hours, as it were.