Why was Moses Denied Entrance to the "Promised Land"?

The chronological approach.  Moses sends out twelve men, one from each tribe, to spy out the land.  They come back with a negative report, speaking of how there were giants in the land and by contrast ". . .we Israelites are as grasshoppers in our sight" (Numbers 13:33).  This report provoked the Lord.  His response:  “And the Lord heard the sound of your words, and was angry, and took an oath saying, ‘Surely not one of these men of this evil generation shall see that good land of which I swore to give to your fathers’” (Deuteronomy 1:34 & 35).  Duly noted exceptions were Caleb and Joshua.

Immediately afterward Moses was tagged with the first prohibition of his entering the land, “The Lord was also angry with me for your sakes, saying, ‘Even you shall not go in there; … (Deut. 1:37).

Many years later with Joshua as his designated successor and just before crossing the Jordan, Moses besought the Lord:  “Then I pleaded with the Lord at that time, saying:  ‘O Lord God, You have begun to show Your servant Your greatness and Your mighty hand, for what god is there in heaven or on earth who can do anything like Your works and Your mighty deeds? I pray, let me cross over and see the good land beyond the Jordan, those pleasant mountains, and Lebanon.  But the Lord was angry with me on your account, and would not listen to me.  So the Lord said to me: ‘Enough of that!  Speak no more to Me of this matter” (Deut. 3:23-26).  Thereafter God gave Moses permission to go to the top of Mt. Pisgah and view the land from a distance.

A helpful commentary.  “There is an acute pathos about the request of Moses the penalty placed upon him.  He had one great commission to fulfill in his life, but he was unable to see its final and victorious conclusion.  This was not due to his own wrongdoing; it was the burden which he had to bear vicariously for the sin of the people for whom he gave his life. . .. God is good, but His election places upon the one called a vicarious burden which has as its purpose the reconciliation of sinners.” (The Interpreter’s Bible, Volume 2, pp. 349, 350).

On at least two notable occasions Moses inserted himself between the wrath of God and the people of Israel, in a very real sense becoming their savior; hence, Moses took their place.  This understanding would play out in Moses being prohibited from entering the land. 

The uncritical approach.  This is reported in the book of “Numbers” and chronologically, appears between the above two instances of prohibition for Moses and happened this way.  The Children of Israel are early in the Wilderness and in great need of water, for them and their livestock.  YHWH tells Moses and his brother, Aaron, to gather the assembly together and “speak” to the rock that water might come forth.  Instead of “speaking” to the rock, Moses, with his rod, smote it twice, prompting this response:  “And the Lord spoke to Moses and Aaron, ‘Because you did not believe Me, to hallow Me in the eyes of the children of Israel, therefore you shall not bring this congregation into the land which I have given them” (Numbers 20:12).

Why the “Numbers” account prevails over that of “Deuteronomy” is to be wondered at.  The essential problem is:  which version is correct.  I prefer the vicarious burden approach.