The Mekhilta debates the physical dimensions of the refuge space that a person who killed accidentally was confined to. The previous passage established that even in the wilderness, a temporary "place" of refuge existed. Now the question becomes: how large was that place?
The Sages propose that the refuge area measured two thousand ells (cubits), roughly half a mile in every direction. But the Mekhilta immediately challenges this figure. Perhaps the space was much smaller, only four ells (about six feet), which is the minimum space a person needs to exist: three ells for his body when lying down and one ell to stretch out his hands and feet. Four ells is the legal minimum of personal space in Jewish law. Perhaps that was all the accidental killer received.
The resolution comes through a gezerah shavah, the same interpretive technique used in the previous passage. The Torah uses the word "place" (makom) in two different contexts. In (Exodus 16:29), the word "place" appears in connection with Sabbath boundaries, which the Sages established as two thousand ells. In (Exodus 21:13), the same word "place" appears in connection with the city of refuge.
Since the same word is used in both verses, the measurement must be the same. Just as the Sabbath "place" extends two thousand ells, so the refuge "place" extends two thousand ells. The accidental killer was not confined to a body-length cell. He had a substantial area in which to live, move, and sustain himself while awaiting the death of the High Priest.
Thus the intent of "I shall make for you a place" was a genuine living space, not a prison cell. The refuge was punishment, not torture. The killer lost his freedom of movement but not his basic human dignity.