There is a doctrine emerging that contends that we must keep all the ordinances of the Old Law, including the feasts, dietary laws, Sabbaths, and even the blood sacrifices. It is an attempt to enhance the New Covenant with an adherence to the Torah. It has rightly been called a "Torah-based Faith".
I have noticed that God established His covenant with Abraham in Genesis 15 by passing through the parts of the sacrifice, the established way to confirm a covenant in the Old Testament (see Jeremiah 34:15). He established the New Covenant in the same way when Jesus Christ passed between the two parts (the thieves) and established His Covenant with mankind when He offered Himself as the only blood sacrifice that can really take away sin. There was no such thing done at Sinai.
I have no desire to argue with those who attempt to approach righteousness through carnal or legalistic means, other than to say that their doctrine is an attempt to nullify the Blood of Jesus, who died to set us free. Rather than argue the point, I will let the Word of God speak for itself. The Bible is very clear on this subject, so I have listed scores of scripture that utterly refute this doctrine of adherence to the Old Law.
Because is a great reference to use when faced with this doctrine because, instead of getting mired in unending arguments that lead nowhere, it simply lists 74 scripture passages straight out of the Word of God to make its point. This is a great way to give someone a simple but effective answer that cannot be argued with.
This book would be a great reference to use in theology classes or Sunday school because most people are not well-versed in these scriptural issues to argue their point. Two Covenants makes the point straight from scripture to not only teach this topic, but also to answer the gainsayers.