Phil Johnson posts a challenging article on legalism noting that:
When it comes to the question of spiritual duties, where Scripture stops speaking, we should, too.
He concludes by saying:
If we add rules that Scripture doesn’t make—especially if we try to impose our manmade rules on other people’s consciences as a standard of spirituality—we are guilty of the same sin as the Pharisees and worthy of the same harsh rebukes Christ leveled at them.
You should read the whole post here.