Why the Wait?!
Why did HaShem wait 3 days until He showed Avraham the place? That’s a long time! Couldn’t HaShem have shown him the correct place right away?
HaShem didn’t want anyone to think that Avraham sacrificed his son on the spur of the moment. So HaShem gave him 3 days, which is plenty of time for Avraham to think about this most important decision. That’s 72 hours, 4,320 minutes, or 259,200 seconds! (Actually, that’s a bit off since it was not 3 complete days. Now you do the math.)
And no, Avraham did not change his mind. He knew that since HaShem is the One who rules the world, he will do whatever HaShem wants, even if it means sacrificing his only son.