What is the allusion to the sentence "a knife fell from the sky"? Did it really appear in ancient times?

In fact, this sentence is only half, and half of the purpose of this sentence is to lead to the meaning of the second half of the sentence. That is to say, even if there is a knife in the sky, I can definitely finish what I want to do when I go out with the lid. It expresses a person's unshakable belief and sense of mission, as well as the sense of responsibility of keeping promises. This sentence is generally only an allusion to determination, because we generally think that knives can't really fall from the sky like rain, but the rich imagination of the ancients can certainly think that the scene of knives falling from the sky is terrible, so it becomes a metaphor. Of course, although we all think that under normal circumstances, it will only rain, snow or hail in the sky, historical records, including modern event records, do have other things falling from the sky, but this kind of thing needs a certain probability. For example, severe weather such as tsunami, strong winds and even tornadoes at sea, in theory, tornadoes are very destructive and can blow a behemoth into the sky. Then, if a sea tornado rolls up the sea water and some marine animals land, it will form a spectacle of fish falling from the sky. This spectacle has indeed happened, especially in modern times. A violent weather activity may cause all kinds of foreign bodies to fall from the sky. Another possibility is that it is not a natural disaster but a man-made disaster. If someone throws a sharp object like a knife from a height, it will really feel like falling from the sky from below. However, in ancient times, there was no such record of a knife really falling in the sky, or there was no real and reliable record, only some dubious folk rumors, which simply could not stand scrutiny. However, from the perspective of scientific theory, we can never predict what a tornado will roll up. If some sharp objects are involved, it will really cause the effect that a knife falls from the sky when it falls, which is completely reasonable. After all, there are many miracles in the world.