John MacArthur helps us understand what it meant that  "He had to suffer to be the perfect author of salvation"  Heb 2:9-10.  In The MacArthur Study Bible, it says:

In His divine nature, He was already perfect.  However, His human nature was perfected through obedience, including suffering in order that He might be an understanding High-Priest, an example for believers, and establish the perfect righteousness to be imputed to believers.