The Israelites are not to use any of the crop until it has been dedicated to the Lord. This is highlighted by naming three kinds of grain: bread, parched grain, and fresh grain. This expresses that the entire crop belongs to the Lord and that he is the one who blesses his people with the harvest.
14 And you shall eat neither bread nor grain parched or fresh until this same day, until you have brought the offering of your God: it is a statute forever throughout your generations in all your dwellings.