מלכים א, פרק י״ז, פסוק ט״ז

The miraculous supply of food in the widow's home was a lasting event. For an entire year, the household was fed without their provisions ever running dry, fulfilling exactly what God had promised [רלב״ג, שטיינזלץ].

The way this continuous supply worked involved a direct, physical change in matter. Rather than the existing food simply stretching, the empty air inside the jar physically turned into flour, and the air inside the jug turned into oil. This literal transformation of one substance into another was similar to the miracle of Moses' staff turning into a snake [רלב״ג]. The unfailing nature of this miracle was specifically focused on the oil itself, which remained continually replenished within its container [מצודת דוד].