Matthew 24:45-51

Who, thinkest thou, is a faithful and wise servant, whom his lord hath appointed over his family, to give them meat in season.

Blessed is that servant, whom when his lord shall come he shall find so doing. Amen I say to you, he shall place him over all his goods. But if that evil servant shall say in his heart: My lord is long a coming: And shall begin to strike his fellow servants, and shall eat and drink with drunkards: The lord of that servant shall come in a day that he hopeth not, and at an hour that he knoweth not: And shall separate him, and appoint his portion with the hypocrites. There shall be weeping and gnashing of teeth.

Luke 12:35-48

For where your treasure is, there will your heart be also. Let your loins be girt, and lamps burning in your hands. And you yourselves like to men who wait for their lord, when he shall return from the wedding; that when he cometh and knocketh, they may open to him immediately. Blessed are those servants, whom the Lord when he cometh, shall find watching. Amen I say to you, that he will gird himself, and make them sit down to meat, and passing will minister unto them. And if he shall come in the second watch, or come in the third watch, and find them so, blessed are those servants.

But this know ye, that if the householder did know at what hour the thief would come, he would surely watch, and would not suffer his house to be broken open. Be you then also ready: for at what hour you think not, the Son of man will come.

And Peter said to him: Lord, dost thou speak this parable to us, or likewise to all? And the Lord said: Who (thinkest thou) is the faithful and wise steward, whom his lord setteth over his family, to give them their measure of wheat in due season? Blessed is that servant, whom when his lord shall come, he shall find so doing. Verily I say to you, he will set him over all that he possesseth. But if that servant shall say in his heart: My lord is long a coming; and shall begin to strike the menservants and maidservants, and to eat and to drink and be drunk:

The lord of that servant will come in the day that he hopeth not, and at the hour that he knoweth not, and shall separate him, and shall appoint him his portion with unbelievers. And that servant who knew the will of his lord, and prepared not himself, and did not according to his will, shall be beaten with many stripes. But he that knew not, and did things worthy of stripes, shall be beaten with few stripes. And unto whomsoever much is given, of him much shall be required: and to whom they have committed much, of him they will demand the more.

Commentary
By St. John Chryostom

...And to me He seems to declare, that at night will be the advent. For this Luke too saith. Seest thou how accurately He knows all things?

After this again, that they may not ask about it, He added, "Watch therefore, for ye know not what hour your Lord doth come." He said not, "I know not," but, "ye know not." For when He had brought them well nigh to the very hour, and had placed them there, again He deters them from the inquiry, from a desire that they should be striving always. Therefore He saith, "Watch," showing that for the sake of this, He did not tell it.

"But know this, that if the good man of the house had known in what watch the thief would come, he would have watched, and would not have suffered his house to be broken up. Therefore be ye also ready, for in such an hour as ye think not the Son of Man cometh."

For this intent He tells them not, in order that they may watch, that they may be always ready; therefore He saith, When ye look not for it, then He will come, desiring that they should be anxiously waiting, and continually, in virtuous action.

But His meaning is like this: if the common sort of men knew when they were to die, they would surely strive earnestly at that hour.

In order therefore that they may strive, not at that hour only, therefore He tells them not either the common hour, or the hour of each, desiring them to be ever looking for this, that they may be always striving. Wherefore He made the end of each man's life also uncertain.