How can a father be told about money taken from him without his knowledge, and does the sin fall away if he does not forgive?

Repentance erases what came before it, except for the rights of human beings. Therefore, the questioner, who has repented from lying and taking his father's money in that manner, should not inform his father of what happened, especially if doing so would lead to harms. He must return what he took to his father as soon as possible when he is able to repay it. However, if death comes to him before repayment, it is hoped that Allah will take it upon Himself to satisfy his father on his behalf.