unexpectedly
—We are very safe and healthy now, but we know that accidents and sickness can come like a thief in the night.

The Bible teaches that Jesus will come back someday to judge all of mankind, but Paul writes that most people will be unprepared for his return:

Now on the topic of times and seasons, brothers and sisters, you have no need for anything to be written to you. For you know quite well that the day of the Lord will come in the same way as a thief in the night. Now when they are saying, “There is peace and security,” then sudden destruction comes on them, like labor pains on a pregnant woman, and they will surely not escape. But you, brothers and sisters, are not in the darkness for the day to overtake you like a thief would. For you all are sons of the light and sons of the day. We are not of the night nor of the darkness.  (1 Thessalonians 5:1-5)