8 But, Brethren, hearken ye and understand, lest any put off to come into the vineyard, because he is sure, that, come when he will, he shall receive this denarius. And sure indeed he is that the denarius is promised him; but this is no injunction to put off. For did they who were hired into the vineyard, when the householder came out to them to hire whom he might find, at the third hour for instance, and did hire them, did they say to him, “Wait, we are not going there till the sixth hour”?
Or they whom he found at the sixth hour, did they say, “We are not going till the ninth hour”? Or they whom he found at the ninth hour, did they say, “We are not going till the eleventh? For he will give to all alike; why should we fatigue ourselves more than we need?” What He was to give, and what He was to do, was in the secret of His own counsel: come when you are called. For an equal reward is promised to all; but as to this appointed hour of working, there is an important question.
For if, for instance, they who are called at the sixth hour, at that age of life that is, in which as in the full heat of noon, is felt the glow of manhood's years; if they, called thus in manhood, were to say, “Wait, for we have heard in the Gospel that all are to receive the same reward, we will come at the eleventh hour, when we shall have grown old, and shall still receive the same. Why should we add to our labour?” it would be answered them thus, “Are you not willing to labour now, who dost not know whether you shall live to old age?
You are called at the sixth hour; come. The Householder has it is true promised you a denarius, if you come at the eleventh hour, but whether you shall live even to the seventh, no one has promised you. I say not to the eleventh, but even to the seventh hour. Why then do you put off him that calls you, certain as you are of the reward, but uncertain of the day? Take heed then lest perhaps what he is to give you by promise, you take from yourself by delay.” Now if this may rightly be said of infants as belonging to the first hour, if it may be rightly said of boys as belonging to the third, if it may be rightly said of men in the vigour of life, as in the full-day heat of the sixth hour; how much more rightly may it be said of the decrepit?
Lo, already is it the eleventh hour, and do you yet stand still, and are you yet slow to come?
Source: Sermons on Selected Lessons of the New Testament (New Advent)