Genesis 12:8

And he went up from thence to a mountain which was eastward of Bethel, and outspread his tent, having Bethel on the west and Ai on the east; and he builded there an altar before the Lord, and prayed in the Name of the Lord.

AND HE CALLED UPON THE NAME OF THE ETERNAL. Onkelos explained it as meaning that he prayed there, just as in the verse, I called upon Thy name, O Eternal, out of the lowest dungeon.
The correct interpretation is that Abraham loudly proclaimed the name of the Eternal there before the altar, informing people of Him and of His Divine essence. In Ur of the Chaldees he taught people but they refused to listen. Now, however, that he had come to the land concerning which he had been promised, And I will bless them that bless thee, he became accustomed to teach and to proclaim the Deity. Scripture likewise tells of Isaac — when he went to the valley of Gerar where he was promised, Fear not, for I am with thee — that he built an altar there and invoked the name of the Eternal, Verse 25. since he had come to a new place where they had not heard of His fame or seen His glory, and he proclaimed His glory among these nations. Now a similar statement is not made concerning Jacob, [i.e., that he proclaimed the name of the Eternal before the peoples of the land of Canaan], for since he begot many children — all of whom were worshippers of G-d — and he had a great community, which was called “the congregation of Israel,” it was through them that the Faith was proclaimed and became known to all people. Besides, the Faith had been proclaimed throughout the entire land of Canaan since the days of his ancestors. In Bereshith Rabbah the Rabbis similarly say, “And he called upon the name of the Eternal. This teaches us that he caused the name of the Holy One, blessed be He, to be in the mouth of all people.”

בית אל מים והעי מקדם, between two large cities, in order to attract large crowds who could hear him preach.

ויעתק משם ההרה, he folded his tent to set out to go to the more mountainous regions east of Bet El, to examine that part of the land, and pitching his tent anew in the area between Bet El and Ai. When arriving there he again built an altar proclaiming the supremacy and uniqueness of the Lord G’d. The ending ה in the word אהלה means the same as the ending ו, i.e. as if the Torah had written אהלו. Avram in “proclaiming” the name of the Lord, issued invitations to the local population to visit this altar, pointing out that this altar was exclusively for serving the Lord and sacrificing to Him. Perhaps the repetition of the words בשם ה' indicates that the people whom Avram invited to his altar were already very close to becoming monotheists. According to Bereshit Rabbah 39,16, quoted by Rashi, he prophesied that at that site or near it, some of his descendants would fall in battle, due to the sin of Achan and members of his family. (Joshua 7,5).

ויט אהלה, “he pitched his tent;” Rashi already comments on the peculiarity of the word אהלה, being spelled with the letter ה at the end, when the pronoun ending for “his” should have been the letter ו. He gives as the reason that the Torah wished us to know that Avraham pitched his wife’s tent before he pitched his own. (based on B’reshit Rabbah). This raises the question why the same word is similarly misspelled in Genesis 9,21 when the subject was Noach’s tent? What are we to deduce from that? We may answer that the reason why the Israelites of the Kingdom of Jerobam, i.e. the ten tribes who had seceded from the Kingdom of David, were exiled, shortly after Solomon had died? According to tradition as spelled out in the Book of prophets, the decree to exile them was sealed because they indulged in debauchery caused by indulging in too much wine too many times. Noach having become too drunk occurred in his wife’s tent, or near its entrance. (Compare Amos 6,6, on the subject of these tribes’ drunkenness) Compare also Ezekiel 23,4: where the word אהליבמה for the capital of that kingdom which had really been Shomron, was changed to indicate that G–d had no place in that kingdom and in its rulers’ considerations. Both the word אהלה and אהליבמה are used by the prophet to describe the disloyal Jews in each kingdom. [The reader is referred to the commentary by Rabbi M. Eiseman in the Art Scroll edition of the Book of Ezekiel, even Jerusalem‘s name being changed in that chapter, as except during the reign of King Chizkiyahu things were not much better in the Kingdom of Yehudah. Ed.]