When Amir was a boy, his father Baba was always giving him advice of one sort or another. Baba liked to portray himself as a paragon of virtue, a veritable font of moral wisdom.
Yet Baba's actions, in complete contrast to his noble words, are anything but morally admirable. In fact, they lay him open to the serious charge of hypocrisy—the very last thing that any self-respecting father wants to be accused of.
First of all, Baba once told Amir that lying is the worst sin. And yet just take a look at Baba's life. He's effectively been living a lie all these years by not revealing that Hassan is his son. Baba certainly treated Hassan like his son but never openly acknowledged that the boy was his own flesh and blood, much to Amir's anger when he finds out the truth.
A further example of Baba's hypocrisy comes when he lectures Amir that when you cheat, you lose the right to fairness. And yet Baba himself is guilty of cheating due to the illicit affair he conducted with Ali's wife, the very same affair that produced Hassan.
This leads us on to a third example of Baba's hypocrisy. He always told Amir that stealing was wrong. And yet he himself has stolen another man's wife by having an affair with her. Stealing is precisely what adultery involves; in moral, if not in legal terms, Baba is just as much of a thief as someone who steals money.