Why did gabrial tell mhammad to go and kill over 700 people?

mohammd headed a army of 3,000 infantry and 310 horsemen after 25 days the non-belivers surrendered. mohammad then tied their hands to their necks and beheaded any male that had began to grow bubic hair.he then divided the among the the men of allah. in the spoils he got safiyah whos husband father had been murdered. she then on the same day. fell in love with the prophet and married him the same day.without going back to my notes can someone give me the sura. and verse of allah. muslims don't need to give one, only dream something up. no offence only the truth.