Abraham's Only Son, I Swear by Myself

At the end of Genesis 22, after abraham doesn't stick the knife in isaac, the angel says a second time. "Because you have done this and have not withheld your son, your only son, i will surely bless you" In other words, my blessing depends on your having done this. Back in chapteri, god says to tell abraham sodom because i want him to teach his children so that they can be blessed through all the nations. Soce: It's very plausible though it goes against two thousand years of interpretations.