Luke 17:36

Two men shall be in the field; the one shall be taken, and the other left.

Two men in the field, one taken and the other left, is part of Christ's warning that the day of the Lord and the judgment will come suddenly. That suddenness is as it was in the days of Noah and of Lot, and it comes as a thief in the night. It falls upon those who are not watching, praying, and working. For that reason the verse is a call to be ready for that day. Readiness means that those who have the light must walk in the footsteps of Jesus and work out their own salvation with fear and trembling.

As with Noah and Lot, this warning about sudden judgment has been given for many years. At first a few responded, while others mocked them, and the people as a whole did not turn to the Lord. When Christ comes in power and glory for judgment, people who have lived and worked together side by side will be separated according to character. Human observers may not see the difference beforehand, but the Lord knows who loves and obeys His commandments. The obedient righteous are the ones taken, to belong to Christ, to join the saints, to enter the city, and to have their names in the book of life. The disobedient are the ones left, for eternal separation from God. At that separation no one can change character for another or have it supplied by another. The wider passage to which the verse belongs also applies to the escape and deliverance of God's people when they flee the cities during the time of trouble while the wicked pursue them.