36 “But as for that day and hour no one knows it—not even the angels in heaven—except the Father alone. 37 For just like the days of Noah were, so the coming of the Son of Man will be. 38 For in those days before the flood, people were eating and drinking, marrying and giving in marriage, until the day Noah entered the ark. 39 And they knew nothing until the flood came and took them all away. It will be the same at the coming of the Son of Man. 40 Then there will be two men in the field; one will be taken and one left. 41 There will be two women grinding grain with a mill; one will be taken and one left.
42 “Therefore stay alert because you do not know on what day your Lord will come. 43 But understand this: If the owner of the house had known at what time of night the thief was coming, he would have been alert and would not have let his house be broken into. 44 Therefore you also must be ready because the Son of Man will come at an hour when you do not expect him.
This is as in that practice of Rabbi Zeira, who, when he would find Sages who were engaging in discussions about the coming of the Messiah, said to them: Please, I ask of you, do not delay his coming by calculating the end of days. As we learn in a baraita: There are three matters that come unexpectly, and these are they: The Messiah, a lost item, and a scorpion.