Ezekiel 33:1KJV

1Again the word of the LORD came unto me, saying,

2Son of man, speak to the children of thy people, and say unto them, When I bring the sword upon a land, if the people of the land take a man of their coasts, and set him for their watchman:

3If when he seeth the sword come upon the land, he blow the trumpet, and warn the people;