In pre-Islamic era, the Pagan Arabs, for the blood-feud of one individual, who was killed from their tribes, would kill as many men and women as they could! They were even willing to massacre a whole tribe to retaliate a single murder of their own clan. This verse and the next make it clear that Islam has mollified the horrors of the pre-Islamic custom of retaliation. Here in the verse, equality and justice, is prescribed with a strong recommendation for mercy and forgiveness; saying if you must take a life for life at least there should be some measure of equality in it.