Abraham the Wall in Nimrod's Furnace and the Call of Lech Lecha

[(Genesis 12:1:) "Now the Lord said to Abram: Go forth."] Rabbi Berekhyah the Priest opened <his discourse> with (Song of Songs 8:8): "We have a little sister." Of whom does the verse speak? Of Abraham. For when Nimrod cast him into the midst of the fiery furnace, up to that point the Holy One, blessed be He, had performed no miracles for him. The ministering angels said before the Holy One, blessed be He: "Master of the World, behold, Nimrod has cast Abraham into the midst of the fiery furnace!" Rabbi Eliezer haQappar said: "We have a little sister" speaks of one who tears and does not mend; but Abraham mended the world before the Holy One, blessed be He. Since up to then he had no children, therefore he is called "sister." "What shall we do for our sister [on the day that she is spoken for]?" (Song of Songs 8:8) — on the day that Nimrod said to cast him into the midst of the fiery furnace. The Holy One, blessed be He, said to the ministering angels: "If she is a wall, we will build upon her a turret of silver" (ibid. 8:9) — [if he gives his life for the sanctification of the Name, we will build upon her a turret of silver]; "and if she is a door, we will enclose her with a board of cedar" (ibid.) — and if he is too poor to give his life for the sanctification of My Name, "we will enclose her with a board of cedar": just as this image which is upon the board is easy to blot out, so is he easy to be lost from the world, and I will not watch over him. Abraham said: "I am a wall" (ibid. 8:10) — "I give my life for the sanctification of Your Name." Immediately he gave his life. How? His father Terah was serving idolatry [and worshiping them]. The Holy One, blessed be He, said to him: "These are idolaters, and you dwell among them — Go forth from your land."