How can we reconcile the acceptance of the highway robber's repentance before being apprehended, as mentioned in Surah Al-Ma'idah (5:33-34), with the Prophet Muhammad's (peace be upon him) disapproval of Usama ibn Zayd for killing a man after he had uttered the Shahadatayn (the two testimonies of faith)?

Repentance is accepted for any sin, and it nullifies the worldly punishment, with details varying according to the sin. Thus, repentance from disbelief (by embracing Islam) absolutely nullifies the worldly punishment. As for the highway robber, his repentance nullifies the prescribed punishment (حد) if it occurs before he is apprehended; otherwise, it does not. However, Imam Ahmad, Al-Shafi'i, and Ibn Taymiyyah hold the view that all prescribed punishments are dropped by repentance before apprehension.