It’s the orginal process of picking wheat. First, you cut and bundle stalks of wheat together. Then you beat the stalks of wheat against a wooden bar to separate the wheat and stalks. Then with a shovel you throw the wheat into the air as the wind separates the chaff from the wheat. The chaff was burned to get rid of it. And wheat is gathered to be used. God used this as a parable, to teach us the process He uses to cleanse us for His use. Wheat is mainly used for bread. Which is the staple of life. Jesus said I am the bread of life. The children of Israel were fed manna, bread from heaven, in the wilderness. Jesus, when tempted by the devil, said that man shall not live by bread alone. But by every word that proceeds out of the mouth of God. We are the wheat and need the be winnowed to be useful to God.