It goes without saying that all religions and all rational people rule that taking others’ lives by assault without any right is unlawful and totally condemned. Given the gravity of this crime, Islam stipulates a severe punishment for he who commits the crime; that is retaliation by killing the murderer only.
Qisas is a divine legislation revealed in the earlier Divine Books. Also, it was the prevalent norm among the Arabs in pre-Islamic era. Though Islam approves of and regulates the principle of Qisas, it stipulates that it should not be carried out in an excessive way. Allah says, “And slay not the life which Allah hath forbidden save with right. Whoso is slain wrongfully, We have given power unto his heir, but
let him not commit excess in slaying. Lo! he will be helped.” (Al-Isra’: 33) Instances of going to extremes in carrying out Qisas are: killing someone other than the murderer, or going beyond the range of those to be killed for murder.
Thus it is clear that none is to be killed in retaliation save the criminal who committed the sin. This is stated in the verse 187 of suratal-Baqarah that you referred to; it reads: “O ye who believe! Retaliation is prescribed for you in the matter of the murdered; the freeman for the freeman, and the slave for the slave, and the female for the female. And for him who is forgiven somewhat by his (injured) brother, prosecution according to usage and payment unto him in kindness. This is an alleviation and a mercy from your Lord. He who transgresseth after this will have a painful doom.” (Al-Baqarah: 178)
Elaborating on the meaning of this verse, the eminent Muslim scholar, Sheikh Muhammad Al-Hanooti, member of the North American Fiqh Council, states:
“Arabs used to believe, because of the tribal system, that a certain family is prestigious over another (for them) humble family. When a person of that inferior tribe murders a dignitary for the upper tribe, they don’t believe that one man who is the killer is enough to be killed for retaliation. The same look was implemented for slaves. A slave of the upper family is not equal to a slave of the lower family. It goes for females also. It this verse, the Qur’an abrogates those jahiliyyah (pre-Islamic) rules and establishes Islamic values, saying to them if a man kills a man, it is enough to punish the murderer on an equal basis as well as any slave who kills another slave, they are equal to each other. The same principles go for a woman.”