John Calvin Commentary Deuteronomy 31:27

"For I know thy rebellion, and thy stiff neck: behold, while I am yet alive with you this day, ye have been rebellious against Jehovah; and how much more after my death?" — Deuteronomy 31:27 (ASV)

For I know thy rebellion. The reason is given why he passed over the usefulness of his doctrine and only cited it as a witness against the Israelites in terms of severity and reproach—namely, because he had found them by experience to be of a "stiff neck" (an expression I have discussed elsewhere), and had no confidence that they would be more teachable in the future. He argues from the lesser to the greater; for, if, while such a leader as theirs was alive, they were rebellious, they were likely to assume greater audacity when he was dead. For we know how effective the authority of a great and excellent person is in restraining the licentiousness of a people. At the same time, Moses does not arrogate so much to himself as to say that the people's good condition depended on his presence, but, pointing out their danger, he seeks to make them more obedient after his death.