Outside: With deepest sympathy
Inside: There are no words however heartfelt that can ease your sorrow but it may strengthen you to realize that those who care for you are close at heart.
When you send a sympathy card or a note of condolence, it is sometimes difficult to know what you should say or how to phrase your thoughts and emotions. The most important thing that you should remember when you write is that your sympathy message comes from the heart. Your friend or loved one is going to appreciate the fact that you acknowledge their grief and honor their loss.