We know that Jesus will return to retrieve His saints. Therefore, we should always be prepared for this earth-wide event.
To that end, the Lord spoke a parable of ten virgins who were to meet the bridegroom, but since he returned during the night, five of the virgins were not ready, having failed to get oil for their lamps. So, they went to buy some when the bridegroom arrived, but Jesus said this,
“And while they went to buy, the bridegroom came, and those who were ready went in with him to the wedding; and the door was shut. Afterward the other virgins came also, saying, ‘Lord, Lord, open to us!’ But he answered and said, ‘Assuredly, I say to you, I do not know you.’ Watch therefore, for you know neither the day nor the hour in which the Son of Man is coming” (Matthew 25:10–13).
The Lord is merciful, but He can also be harsh for those who have failed to prepare for His return. For that reason, He taught us to prepare ourselves for His arrival at any time, because we do not know the day or the hour of when He shall return.