Why Moses did not enter the Promised Land?

Moses was a "divinely appointed child." He was born in Egypt, being the son of Amram, the grandson of Kohath and the great-grandson of Levi. His mother Jochebed was Kohath's sister. Moses was three years younger than his brother Aaron. Miriam their sister was some years older.

Moses' life was spared from Pharaoh's genocidal decree commanding the destruction of every newborn Hebrew male. He was hidden by his mother for three months, then placed in a papyrus ark on the Nile River, where Pharaoh's daughter found him. Through the courageous action of his mother and sister, Moses came to be nursed and trained by his mother because she was hired by the Pharaoh's daughter as a nurse, given the fact that she adopted the child as  her son.

In his early life as a member of Pharaoh's household he was "instructed in all the wisdom of the Egyptians," becoming "mighty in his words and deeds," powerful in both mental and physical capabilities. Ex.2:1-10; Acts 7:20-22. In spite of his favored position, Moses' heart was sincerely united with the roots of his real parents, the hebrews.  In fact he was hoping to be used by God to bring deliverance to their people from the burdens they were bearing in the land of the Egyptians.

In the fortieth year of his life, he saw an Egyptian striking a Hebrew. In taking up his fellow brother's defense he killed the Egyptian and buried him in the sand. Actually, Moses felt that the time had come that he, as a man of great power, would be able to give the Hebrews salvation. But the people was not ready and God's due time had not yet arrived. Moses' plan did not work out and he was forced to flee from Egypt when Pharaoh heard of the slaying of the Egyptian. Ex.2:11; Heb.11:24-26.

Moses had to undergo another forty years of training. The qualities of patience, meekness, humility, long-suffering, mildness of temper, self-control and learning to wait on God's due time, needed to be developed in him. He had to be prepared to endure the discouragements, disappointments and hardships he would encounter, and to handle with loving-kindness, calmness and strength the multitude of problems a nation would present.

It was while Israel was encamped at Kadesh, at the extremity of Edomite territory, in the fortieth year of their wanderings that he made a serious mistake. The fact that he not only was in a highly powerful and privileged position, but under very heavy responsibility as leader and mediator to God for the nation, Moses was supposed to endure against the attack of the devil putting up with the perverseness and insubordination of the nation. Instead, he sinned against God. Exasperated and embittered in spirit, he an his brother Aaron stood before the people as God commanded, but instead of calling attention to God as the Provider, they directed the attention of the nation to themselves. 

Later God decreed: "Because you did not show faith in me to sanctify me before the eyes of the sons of Israel, therefore you will not bring this congregation into the land that i certainly give them." Num.20:1-13; Deut.32:50-52; Ps.106:32,33.