This seems to be a common misconception that is often read into Paul's writings. If you give me the verse you're referring to I'll give you my opinion on it.
The arguments over how much of the Jewish law to follow goes back to the council in Jerusalem, where Paul argued that change of heart was the main thing necessary, not following rigid rules.
Essentially that's true. On our own we couldn't hope to follow God's laws, but with Christ all things are possible.
Christians to this day continue to argue over these things, but as he pointed out in Romans, we should not do so.
Verse?