Five things are obligated in challah: wheat, barley, spelt, oats, and rye. These [species] are obligated in challah, they combine with one another and they are forbidden under [the law of] chadash [to be eaten] before Pesach, and to be harvested before the omer. And if they took root before the omer, the omer renders them permitted; but if not, they are forbidden until the next omer is brought.