The deception in both circumstances was not that Sarah/Sarai was Abraham's/Abram's sister. The deception was that Sarah/Sarai was not Abraham's/Abram's wife. Lots of cultures married their sisters--if she had been both his sister and his wife, that would have been shruggable.
The deception was that she was free to be taken in marriage. People today--unfortunately even Christians-- like to define "lie" according to whether the words depict physical facts--that's Greek epistemology. We in the West are steeped in Greek epistemology.
But God doesn't do Greek epistemology. The fact is that Abram/Abraham used clever wording to deceive two leaders, and God called him on it both times.
Then you have to conclude that Jesus lied by hiding the fact that He was God to many people. He did not reveal a very important truth to people. Jesus specifically told his disciples shortly after Peter said that he was the Son of God, that they should tell no man that he was Jesus the Christ (i.e. the Messiah).
"Then charged he his disciples that they should tell no man that he was Jesus the Christ." (Matthew 16:20).
Jesus also at certain times told people to not tell anyone of the miracles that He was doing.
Jesus deflected the Pharisee's claim against Jesus in the fact that He was claiming to be God.
In reply: Jesus quoted the Old Testament Scripture to them that says, "Ye are gods"? (Which was in reference to the Israelites in being rulers).
Jesus had a mission to protect and to fulfill.
So He could not reveal all truth to everyone.
Not revealing all truth to a person does not mean you are lying.
It is still true that Abram's sister was Sarai.
That was not a lie.
Abram chose to not reveal the truth that she was his wife.
Not revealing a truth is not the same as telling a bold face lie.
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