According to the word of the Lord - It denotes that Moses died, not because his vital powers were exhausted, but by the sentence of God, and as a punishment for his sin. Compare Deuteronomy 32:51.
Related Commentaries of Deuteronomy 34:5
Deuteronomy 34:5
5 So Moses the servant of the LORD died there in the land of Moab, according to the word of the LORD.