If It Was a Sin, Why Did He Do It Again? #Shorts

First of all, says the Maral, if it's true that it was decreed on Abraham that his descendants should have to go down to Mitzrayim because Abraham sinned by telling the Pharaoh that they're brother and sister, so could you tell me why shortly after when Abraham went to Gerar and Avimelech says, "Who's the lady?" and Abraham says, "She's my sister." Why would he repeat the same thing? If it was such an egregious sin, then why did Abraham Avinu do it again? And guess what Yitzchak did when he went down with Rivka. See, Abraham was polite. Abraham said, "Sarah, here's the deal. When we go down, you're going to say we're brother and sister." When Yitzchak went with Rivka, he took no chances. Paroh says to Rivka, "Rivka, who are you?" Yitzchak's like, "Hey, you know, she's my sister." He didn't even ask her before. So, if such an egregious sin, why did Abraham Avinu Avinu repeat it? And why did Yitzchak