Noun
the way of proper and honest behavior
Source: WordNetFor a good man to realize that it is better to be whole than to be good is to enter on a strait and narrow path compared to which his previous rectitude was flowery license. John Middleton Murry
Now the passage being very strait and narrow... I was well nigh quite beat out, by striving to get in. John Bunyan
he taught his children to keep strictly to the straight and narrow Source: Internet