Simply to feed the birds... there may be some obsure religious reason though but I really doubt it.
Grain is tied in sheaves.
The collective word for 12 sheaves of grain is a "gross." In agricultural terms, a gross typically refers to a quantity of 144, but specifically for sheaves of grain, it can denote a smaller grouping like 12. This term is often used in contexts involving farming and harvesting.
Stook or stack
Sheaf may be the term you're looking for. Sheaves of grain are bundles of grain before threshing.
Tying up bundles of freshly cut wheat or other grain.
A sheaf is how you stack grain so that it sheds water and stays fresh until you need to use it. The stalks are placed vertically, leaning against one another to make a tall mushroom-shaped structure.
Sheaf may be the term you're looking for. Sheaves of grain are bundles of grain before threshing.
"Sheaves" is the plural of "sheaf," which the dictionary defines as "a bundle of cut stalks of grain or similar plants bound with straw or twine." The premise of the hymn is based on Jesus' comparison between a harvest of grain and people being "brought into" the kingdom of God. Luke 10:2 - Then He said to them, "The harvest truly is great, but the laborers are few; therefore pray the Lord of the harvest to send out laborers into His harvest."
Ruth was destitute, so she gleaned fallen grain-sheaves in the fields of others.
A bundle of wheat is called a sheaf. The plural is sheaves.
In "Little House in the Big Woods," Pa gathered grain by using a process called "harvesting." He would cut down the ripe grain with a scythe and then bind it into sheaves. Afterward, he would stack the sheaves in a safe place to dry before threshing the grain to separate it from the chaff. This labor-intensive process was essential for providing food for the family.
It depicts a pine tree with fourteen branches, a cow as a tribute to its dairy history, two sheaves of grain and a forest.