From the early Church Fathers to now.
“Watch ye therefore, because ye know not what hour your Lord will come.”
“Those of more plain understanding say, that He spoke this of His second coming; but others would say that it applies to an intellectual coming of the word into the understanding of the disciples, for as yet He was not in their understanding as He was to be.”
“The master of the household is the understanding, the house is the soul, the thief is the Devil. The thief is also every contrary doctrine which enters the soul of the unwary by other than the natural entrance, breaking into the house, and pulling down the soul’s natural fences, that is, the natural powers of understanding, it enters the breach, and spoils the soul. Sometimes one takes the thief in the act of breaking in, and seizing him, stabs him with a word, and slays him. And the thief comes not in the day-time, when the soul of the thoughtful man is illuminated with the Sun of righteousness, but in the night, that is, in the time of prevailing wickedness; in which, when one is plunged, it is possible, though he have not the power of the sun, that he may be illuminated by some rays from the Word, as from a lamp; continuing still in evil, yet having a better purpose, and watchfulness, that this his purpose should not be broken through. Or in time of temptation, or of any calamities, is the time when the thief is most found to come, seeking to break through the house of the soul.”
“He would have them ever ready, and therefore He says, Watch.”
“In this He rebukes such as have less care for their souls, than they have of guarding their money against an expected thief.”
“Having declared that of that hour knoweth no man, but the Father only, He shews that it was not expedient for the Apostles to know, that being ignorant they might live in perpetual expectation of His coming, and thus concluding the whole, He says, Watch therefore, &c. And He does not say, ‘Because we know not,’ but Because ye know not, shewing that He Himself is not ignorant of the day of judgment.”
“And by the instance of the master of the household, He teaches more plainly why He keeps secret the day of the consummation.”
“(Ep. 199, 3.) He said this Watch, not to those only who heard Him speak at the time, but to those who came after them, and to us, and to all who shall be after us, until His second coming, for it touches all in a manner. That day comes to each one of us, when it comes to him to go out of the world, such as he shall be judged, and therefore ought every Christian to watch that the Lord’s coming may not find him unprepared; and he will be unprepared for the day of His coming, whom the last day of his life shall find unprepared.”
“(non occ.) Foolish are all they, who either profess to know the day of the end of the world, when it is to come, or even the end of their own life, which no one can know unless he is illuminated by the Holy Spirit.”
“(Hom. in Ev. ii, 3.) To watch is to keep the eyes open, and looking out for the true light, to do and to observe that which one believes, to cast away the darkness of sloth and negligence.”
“(Hom. in Ev. xiii. 5.) Or, the thief breaks into the house through the neglect of the master of the house, when the spirit has slept upon its post of guard, and death has come in unawares into the dwelling house of our flesh, and finding the lord of the house sleeping, slays him; that is, the spirit, little providing for coming evils, is taken off unprepared, to punishment, by death. But if he had watched he would have been secure from the thief; that is, looking forward to the coming of the Judge, who takes our lives unawares, he would meet Him with penitence, and not perish impenitent. And the Lord would therefore have the last hour unknown, that it might always be in suspense, and that being unable to foresee it, we might never be unprepared for it.”
The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.