I've written before about the words we use to talk about the Old Testament. And currently there is something of a trend to call the Old Testament either the Tanakh or the Hebrew Bible. I won't repeat the earlier post, but I did want to add: it is sometimes important for us as Christians to be able to affirm that the Old Testament is, in fact, old. We no longer look for a human priest to make animal sacrifices, or for animal blood to be thrown on an altar. We Christians can be thankful that we never again desire animal sacrifices: they are old, their day has gone, and we do not want their return. We no longer say that some food can make a person unclean -- because we affirm that what defiles a person is what comes from their heart. We no longer say, "An eye for an eye and a tooth for a tooth" as did the Torah, and the code of Hammurabi before it.
There are times when we may prefer to call the Old Testament by the name Tanakh. But there are times when it is necessary to affirm that we see it as old: the days of blood sacrifice are gone, the days of "an eye for an eye and a tooth for a tooth" are gone, the days of a nation being asked to eradicate its neighbors for their religious beliefs are gone. When we call it the "Old Testament" we proclaim our belief that those days are gone. The fact that those days are gone is part of the good news.
"If those things are part of your holy book, then how can you say they are not part of your religion?" Because they are old: the old has gone and the new has come.