What did Abraham do wrong with Sarai in Egypt?
Abraham told Sarai to say she was his sister, not his wife, when they went down into Egypt, because he feared the Egyptians would kill him to take her. That deception was sin. God did not cast him out, but Abraham had to recognize his sin.
Les explains that Abraham, with his beautiful wife Sarai, went down into Egypt and feared the Egyptians would want her in their harem and kill him. So he told her to say she was his sister, not his wife. Les says that was sin. Yet God did not kick Abraham out; he had to recognize his sin as a believer. Les parallels this with Peter, whom Jesus prayed for lest his faith fail when Satan sifted him; Peter denied Jesus to a teenage girl, the cock crowed, and he wept bitterly because he was convicted. It did not throw Peter out; he was reconciled immediately when he confessed. Les adds that Paul's doctrines of grace never give license to sin, and John writes that we should not sin, but if we do, confession restores.