Translation of the verse 15 from Surah Al-Qasas : Number of verses 88 - - page 387 - Part 20.
And he entered the city at a time of unawareness of its people, and he found there two men fighting, - one of his party (his religion - from the Children of Israel), and the other of his foes. The man of his (own) party asked him for help against his foe, so Musa (Moses) struck him with his fist and killed him. He said: "This is of Shaitan's (Satan) doing, verily, he is a plain misleading enemy."
And he entered the city at a time of inattention by its people and found therein two men fighting: one from his faction and one from among his enemy. And the one from his faction called for help to him against the one from his enemy, so Moses struck him and [unintentionally] killed him. [Moses] said, "This is from the work of Satan. Indeed, he is a manifest, misleading enemy."
(28:15) (One day) he entered the city at a time when the people were heedless. *20 There he saw two men fighting, the one of his own people, the other of his enemies. The one belonging to his own people asked his help against the one belonging to the enemy. Moses gave him a blow *21 and killed him. (On seeing what had happened) Moses said, "This is the work of Satan: he is a deadly enemy (of man) and an open misleader." *22
*20) It might be the early morning, or midday in summer, or night in winter, when the roads were deserted and there was all quiet in the city. The words "entered the city" indicate that the royal palaces were situated outside the capital, away from the common population. The words used are "entered the city" and not "came out in the city", because the Prophet Moses lived in the royal palace.
*21) The word wakaza in the original means both giving a slap and giving a blow. We have adopted "Moses gave a blow" for the reason that a blow can cause death but not so a slap.
*22) One can imagine the state of utter remorse and confusion in which the Prophet Moses uttered these words when he saw the Egyptian fall down after receiving the blow and breathe his last. He had no intention to murder, nor is a blow struck to kill, nor can one expect that a healthy person would die on receiving a blow. That is why the Prophet Moses exclaimed: "This is the work of Satan! He has made me do this in order to work some great mischief, so that I am accused of killing an Egyptian while defending an Israelite, and a violent storm of 'anger and indignation is aroused in the whole of Egypt not only against me but the whole Israelite community." In this connection, the Bible gives a different version from the Qur'an. It declares the Prophet Moses to be guilty of wilful murder. It says that when Moses saw an Egyptian and an Israelite fighting, "He ( Moses) looked this way and that way, and when he saw that there was no man, He slew the Egyptian, and hid him in the sand." (Exod. 2: 12). The same is the version of the Talmud also. Now anybody can see how the Israelites brand the characters of their elders with infamy and how the Qur'an exonerates them. The verdict of common sense also is that a wise and discreet person, who was to become a great Prophet in the future, and who had to give man a great code of law and justice, could not be such a blind nationalist that seeing a member of his own community fighting with a man of the other community he would be so infuriated that he would kill the other person wilfully. Evidently, it could not be lawful to kill the Egyptian only for the sake of rescuing an Israelite from his tyranny.