If they see that you have a real emotional commitment to something, it's more likely that the issue will become important to them, too. He's crying because you took his toy away. Be frank, honest and upfront with your kids about what kind of behavior you do and don't like. In other words, actions speak louder than words. If you are consistently caring and compassionate, it's more likely that your children will be too.
Children watch their parents, and other adults, for clues on how to behave.
Keep in mind that if you say one thing and do another, your children will pay a lot more attention to what you do. The old warning 'Do as I say, not as I do' simply does not work, particularly when it comes to teaching about caring. Not everyone has time to devote to volunteer work or money to donate to causes, but there are small acts of caring that can be part of your family's life. These acts of caring don't have to be grandiose. Try to surround your children with other people who are kind and caring, so that they have several role models.