'Alert' in the Bible

Watch out! Be alert, because you do not know when the time is!

It is like a man away on a journey, who left his house and gave his slaves authority--to each one his work--and to the doorkeeper he gave orders that he should be on the alert.

Therefore be on the alert, for you do not know when the master of the house is coming--whether in the evening, or at midnight, or when the rooster crows, or early in the morning--

And what I say to you, I say to everyone: Be on the alert!"