Charles Ellicott Commentary Exodus 21:19

"if he rise again, and walk abroad upon his staff, then shall he that smote him be quit: only he shall pay for the loss of his time, and shall cause him to be thoroughly healed." — Exodus 21:19 (ASV)

If he rise again, and walk abroad upon his staff. — The charge of murder was not to be kept hanging over a man indefinitely. If the injured person recovered sufficiently to leave his bed, and get about with the help of a stick, the injurer was to pay his fine and be cleared of his offense, whatever might happen afterwards.