John Gill Commentary Ezekiel 33:3

"if, when he seeth the sword come upon the land, he blow the trumpet, and warn the people;" — Ezekiel 33:3 (ASV)

If what he sees the sword come upon the land Or those that kill with the sword, as the Targum; as soon as he observes a body of armed men, more or less, marching towards the borders of the land with a manifest intention to enter and invade it:

he blow the trumpet, and warn the people ; warn the people by blowing the trumpet, the signal agreed on; by which they would understand that an enemy was at hand, or danger near; or warn them by word of mouth, as well as by the trumpet, where he could do it, and when it was necessary.