“Like a grain that produces seven ears” (al-Baqarah 2:261).
The parable illustrates the multiplication of reward for giving. Grain, ears and seeds form a vivid picture. Understanding the moral teaching does not require proving that every ordinary grain always yields the depicted quantities under all conditions.
An illustration is interpreted through the comparison it is designed to convey. Every pictorial detail need not be imposed as a literal requirement on every real-world instance or beneficiary of the rule.