Practice v Scripture
From dKosopedia
A common mistake of the armchair student of religion is to assume that religious practice is strongly connected to the leading scriptures of that religion. This simply is not the case. Every religion has a substantial "tradition" that connects the two, sometimes written and sometime not.
For example, anyone reading the Christian Gospels would naturally assume that faith healing is one of the primary sacraments and activities of Christian clergy, and that Christians universally see demon possession as a major cause of disease. The Gospel of Mark, for example, has more episodes of faith healing than it does parables. In fact, it is a quite rare practice in most "liturgical" churches.
Likewise, an individual reading the Hebrew Bible in isolation might come to the incorrect conclusion that animal sacrifice is a central part of the living Jewish faith, and the Jewish religious life is largely organized around a Temple. Neither has been true for millenia, but no one reading this scripture would know this fact.
Similar caution is in order when attempting to discern Islamic, Hindu, Buddhist or other forms of religious practice from the relevant holy texts. Written scriptures have a strong tendency to "cap off" at some point in time and to remain virtually unchanged once an accepted manuscript has emerged. In contrast, religious practice necessarily evolves from generation to generation, and continues to the present day.
For example, in 1950, almost no predominantly white churches in the United States (predominantly black churches have long been more contemporary in their musical choices) used contemporary music during church services. Lutherans sang hymns that dated to the Reformation. The Catholics didn't even sing their ancient liturgy in the vernacular; they used Latin. And, other religious denominations in the United States were hardly more innovative. Today, half a century later, only a minority of predominantly white churches (Catholic and Protestant alike), lack contemporary musical services as at least part of their ministry, and some lack the "traditional" musical arrangements associated with their denomination or its predecessors entirely.