When I think of Moses, what comes to mind first is that he is a man who witnessed so many miracles: the 10 plagues of Egypt, each of them being mind-blowing in and of themselves, there was the crossing of the Red Sea afterwhich witnessing the destruction of the enemy, there were the initial signs of Moses to the people of his staff turning into a snake then not, and him causing his hand to become leprous then not, and there were the times when God miraculously provided water, then the manna and then even meat.

Over and over God clearly demonstrated Himself as being with Moses, in each one of the above.  Without a doubt.  Even the Egyptians eventually feared Moses.

All of that is why the following caused me one time to take a step back in my thinking.  This was when Moses was initially approached by God at the burning bush in Exodus 3:12.  

And He (God) said (to Moses), "Certainly I will be with you, and this shall be the sign to you that it is I who have sent you: when you have the brought the people out of Egypt, you shall worship God at this mountain."

I had read that verse numerous times over the years.  Then one time I read it as if for the first time.  Coming to the base of Mount Sinai with the children of Israel to worship before the presence of God . . . that was suppose to be THE sign that God was with Moses?   Getting across that desert land to Mt. Sinai after all of those miracles seemed to me to be just a bit . . . anticlimatic.  Those miracle events included even the Passover.

At some level I didn't get it.  It was like the Holy Spirit was letting me know that there was something in that statement that I didn't see.  It bugged me.  Why would God put the emphasis there?  Yes, blah, blah, blah, I understand.  All of those prior miracles led up to the meeting at Mt Sinai.  Yet, still, if you were Moses, wouldn't you have concluded that God was indeed with you when, for example, the crossing of the Red Sea took place?   If you could drop a staff into being a snake and then pick it back up by the tail for it to become a staff again, would you need any other miracle?  OK, fine, Pharaoh's magicians could do the snake thing.  But what about after you brought a plague of boils on everybody, their butt cheeks included?  Would be wondering then?  See what I am getting at?

Why would God tell Moses that getting the people to the mountain was THE sign that God was with him?

Recall what Moses told the people of Israel in Deuteronomy 18:15, "The LORD your God will raise up for you a prophet like me from among you, from your countrymen, you shall listen to him."  

Some types/shadows in the scriptures are expressed to us clearly.  Moses is a picture of Jesus.  Moses' interactions with God give us a glimpse into Jesus' relationship with His heavenly Father, providing clues into aspects of their intimacy not only in their plan to rescue us, but even during Jesus' incarnation on earth.

Take a moment to absord/comprehend the level of trust it would take for Jesus to become incarnated.

Imagine you are chosen to infiltrate enemy territory during a war.  The plan would include all of your memories to be wiped out.  You would wake up in enemy territory without a clue as to it even being an enemy territory.  At that moment, when you became conscious in enemy territory, any skills you would have mastered prior would be gone, any sophisticated intel you had memorized would be a total blank.  Your country would be solely relying upon who you were in terms of your character alone.  It would be up to those on your side, over time, to find you, to gain your trust, to teach you what you needed to know and to do, to reveal the enemy to you, and to convey the plan you had helped to create prior so as to overturn the enemy's seeming victory into total defeat once and for all.

Absolute and total vulnerability and dependance.

So, I find in my trying to understand the prophecies of the scriptures that there is a benefit to think first and foremost in terms of the extreme love that exists between the Father and His Son.  The Old Testament scriptures contain a lot of information that the Holy Spirit revealed to Jesus when He was growing up, about who He was, who the Father was, who the enemy was, and what their plan was.  Of course, the Old Testament is about Jesus.  That is so much how the Father taught His Son.

This would have included Moses.  Jesus would have come to seek, at some point, that Moses was about Him.

I believe that is why Exodus 3:12 is worded the way it is!!!   THE sign from the Father to the Son that He would be with Him will be the gathering of a chosen people before a Mt. Zion in heavenly places, in the presence of our God at some future date!  They were going to be completely successful!

When?

Perhaps the same date as indicated in Exodus 19:1.

This year that happens to be, per the popular Jewish calendar, as sometime during June 19-23rd.