Numbers 27:12-14
And the LORD said unto Moses, Get thee up into this mount Abarim, and see the land which I have given unto the children of Israel.  And when thou hast seen it, thou also shalt be gathered unto thy people, as Aaron thy brother was gathered.  For ye rebelled against my commandment in the desert of Zin, in the strife of the congregation, to sanctify me at the water before their eyes: that is the water of Meribah in Kadesh in the wilderness of Zin.

As great as Moses was, as closely as he walked with God, as much as he experienced in the presence of God, and all that he saw and did, he was still a man of flesh capable of rebelling against God.  He was a godly man, but he was not a perfect person.  He knew the law of God well.  He knew God well.  He knew what God wanted him to do.  But that didn’t erase his sin nature or that inherent weakness that resides within all of mankind.  And indeed, Moses had to face a harsh consequence for what he had done.

No one is incapable of sin and disobedience.  As much as we may desire to obey, no matter how much we love God and know Him and His Word, we’re still going to end up failing Him at different times and to different degrees.  Sometimes our emotions or our frustrations or our circumstances get the best of us, and in a moment of weakness, we sin, and there’s no taking it back and no undoing what we’ve done.  And even if others contributed to it, we bear the effects of our own choices.

Surely this was a moment of regret for Moses, and he’d had others in his life.  But that didn’t prevent him from continuing to move forward, to keep following the Lord.  He’d remained faithful to his calling, to God’s law, and to the people of Israel.  He gave Himself fully to what had yet to do and then accepted God’s will for the end of his life.  As difficult as it may have been, he was willing to bow to God’s sovereignty.

No human on Earth is infallible, no matter how strong their spiritual life is, no matter how much they are used by God, no matter how wise.  Only one—Jesus Christ—lived a perfect and sinless life.  We can’t think of anyone, even ourselves, as incapable of sin and rebelling against God and disobeying Him.  But we can seek His forgiveness, accept the consequences with grace, and keep moving forward as God continues to lead us and use us despite our weakness.