It seems common sense that motive is an important part of ethics. It almost seems to go without saying that why we do something is often very important in understanding whether an action is good or bad.
Interestingly the idea that motive matters in ethics is under attack by many of today's philosophies. They seem to equate that the result rather than the motive is what is important.
There does seem to be a certain value in placing result as the primary evaluation of ethics rather than motive, since a lot of people seem pretty confused about what it means to be a good person. The Bible clearly shows that ethics consists of many elements one of which is motive.
The practical applications are many of motive as a part of ethics. The bible frequently talks about not pushing forward ones good works. Why? The motive of pride spoils most of the ethical nature of works.
A phrase which is fairly common, but holds a lot of value is "speaking the truth in love." It is easy to think that simply speaking the truth is loving, but the reality is that there is a huge amount of discernment needed in when to speak the truth and when to wait for a better moment or when to say nothing at all.