Ezekiel 33:1-3

1And the word of Jehovah 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, and the people of the land take a man from among them, and set him for their watchman;

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