Question: what to say to a friend whose dad passed away?
Answer: My heartfelt condolences. ... 
Your father always bragged about how wonderful you were. ... 
Your father was one of the nicest people I know and I know that he was a great dad too. ... 
I am truly sorry for your loss. ... 
No matter wherever he is, he'll always be watching over you. ... 
I was so sorry to hear about your father's passing.