‘And it happened that when he was on the verge of entering Egypt he said to Sarai his wife, “Look now, I know that you are a very beautiful woman. And when the Egyptians see you they will say ‘this is his wife', and they will kill me and save you alive. I beg you, say you are my sister so that it may be well with me for your sake, and that my soul may live because of you'.” '
Sarai's beauty must have been exceptionally outstanding for Abram to have this fear, for he would have had his retainers with him. But he has clearly heard rumours about the way Egyptians sometimes treated ‘foreigners' and her beauty fills him with apprehension.
The Egyptians undoubtedly despised foreigners and saw themselves as ‘men', and foreigners as mere ‘humans', until they learned to speak Egyptian. Abram had nothing to judge the Egyptians by except hearsay for he knew nothing about Egypt except for what he had been told, but he knew that they were a powerful nation and famine would have left him and his retainers somewhat weak and frail. They were after all coming to beg for help.
Furthermore we learn later that this habit of describing Sarai as his sister was a policy he had settled on long before when he first ‘left his father's house' (Genesis 20:13). The statement was true in terms of those days. She was in fact his half-sister (Genesis 20:12). In fairness to Abram it must be recognised that while this was undoubtedly because he was concerned for his own life he also has in mind Sarai's safety. He no doubt thought that if men killed him for his wife, his wife would become their plaything. But if they saw the opportunity of wooing Sarai respectably they may well treat Abram well with a view to a respectable marriage, giving them the opportunity to move on in safety.
The plan may have worked well elsewhere but here it misfired. What he could not have foreseen (because he was not familiar with great kings and their ways) was the policy of Pharaoh to have men constantly on the lookout for beautiful women for his harem.