NOTES for Gen 12:1-4
Abraham is 75 years old. However one regards that number, he is plainly already at an unsuitable age to pull up stakes and go into the unknown. If we remember other examples, Peter is over forty, an age when it is considered that a person should have everything settled. John, on the other hand, is far too young to decide anything.
Whoever we look at, there is no age suitable for answering the voice of God. We can never be responsible enough, wise enough, good enough to get up and go to the mountain, to another land, into complete uncertainty, in order to see what it is not yet possible even to speak about.