What Obi-Wan said:
Your father wanted you to have this when you were old enough: … Your father’s lightsaber.
What Obi-Wan meant:
Actually I just grabbed this off the ground from where your father dropped it after I cut off his legs and left him for dead in a lava pit. His final words to me were “I hate you!” But since he wasn’t aware of your existence, he didn’t say anything about NOT giving you this later on. So what I told you was true – from a certain point of view.