I am not satisfied with EoI s summary It shows the Muslim view as a static thing it does not show how the substitutionist idea evolved over time e g all the variant stories of the substitutionist idea were related by Tabari on the behalf of a certain Jewish and an unnamed Christian convert to Islam people thought that a person being killed on the behalf of another is injustice so the person must have done it voluntary later stories said that it was a form of punishment for the other person thus we have Judas Iscoriot coming into play then we have al Zamashkari who said that the substitutionist idea can not possibly fit the relevant quranic verse based on grammatical consideration then comes Razi s criticism of the substitutionist idea For many mutazila the idea of God committing acts of injustice was repugnant furthermore for God to allow confusion of identity for whatever reason was irrational and inadmissible It is therefore not God who caused that but the Jews who took another person themselves and killed him not letting people to come close and see what s going on Then came the modern scholars such as the author of al manar who try not to talk about what really happened saying that the verse is obscure mutashabihat In any case there are a lot of sources and I don t think the current version is satisfactory