A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
gen 12:1CALL TO ABRAM. (Gen. 12:1-20)
Now the Lord had said unto Abram--It pleased God, who has often been found of them who sought Him not, to reveal Himself to Abraham perhaps by a miracle; and the conversion of Abraham is one of the most remarkable in Bible history.
Get thee out of thy country--His being brought to the knowledge and worship of the true God had probably been a considerable time before. This call included two promises: the first, showing the land of his future posterity; and the second, that in his posterity all the earth was to be blessed (Gen 12:2). Abraham obeyed, and it is frequently mentioned in the New Testament as a striking instance of his faith (Heb 11:8).
gen 12:5into the land of Canaan . . . they came--with his wife and an orphan nephew. Abram reached his destination in safety, and thus the first promise was made good.
gen 12:6the place of Sichem--or Shechem, a pastoral valley then unoccupied (compare Gen 33:18).
plain of Moreh--rather, the "terebinth tree" of Moreh, very common in Palestine, remarkable for its wide-spreading branches and its dark green foliage. It is probable that in Moreh there was a grove of these trees, whose inviting shade led Abram to choose it for an encampment.
gen 12:7Unto thy seed will I give this land--God was dealing with Abram not in his private and personal capacity merely, but with a view to high and important interests in future ages. That land his posterity was for centuries to inhabit as a peculiar people; the seeds of divine knowledge were to be sown there for the benefit of all mankind; and considered in its geographical situation, it was chosen in divine wisdom as the fittest of all lands to serve as the cradle of a divine revelation designed for the whole world.
and there builded he an altar unto the Lord--By this solemn act of devotion Abram made an open profession of his religion, established the worship of the true God, and declared his faith in the promise.
gen 12:10there was a famine . . . and Abram went down into Egypt--He did not go back to the place of his nativity, as regretting his pilgrimage and despising the promised land (Heb 11:15), but withdrew for a while into a neighboring country.
gen 12:11Sarai's complexion, coming from a mountainous country, would be fresh and fair compared with the faces of Egyptian women which were sallow. The counsel of Abram to her was true in words, but it was a deception, intended to give an impression that she was no more than his sister. His conduct was culpable and inconsistent with his character as a servant of God: it showed a reliance on worldly policy more than a trust in the promise; and he not only sinned himself, but tempted Sarai to sin also.
gen 12:14when Abram was come into Egypt--It appears from the monuments of that country that at the time of Abram's visit a monarchy had existed for several centuries. The seat of government was in the Delta, the most northern part of the country, the very quarter in which Abram must have arrived. They were a race of shepherd-kings, in close alliance with the people of Canaan.
gen 12:15the woman was taken into Pharaoh's house--Eastern kings have for ages claimed the privilege of taking to their harem an unmarried woman whom they like. The father or brother may deplore the removal as a calamity, but the royal right is never resisted nor questioned.
gen 12:16he entreated Abram well for her sake--The presents are just what one pastoral chief would give to another.
gen 12:18Here is a most humiliating rebuke, and Abram deserved it. Had not God interfered, he might have been tempted to stay in Egypt and forget the promise (Psa 105:13, Psa 105:15). Often still does God rebuke His people and remind them through enemies that this world is not their rest.